First, if the seller advertised it as in "unknown condition", what makes you think it had any word processing programs on it? In the System 6 era, TeachText (as it was then known,) wasn't a default install.
For most programs, you install by just dragging the icon from the floppy to the hard drive, especially programs that were designed to run directly from their floppy. For some program (especially large programs that come on multiple disks, like Microsoft Word,) you do have to run an installer.
One thing to find out is if it has an 800k (Double Sided, Double Density, also incorrectly called 'low density',) floppy drive or a newer 1.4 MB drive (High Density, or "SuperDrive".) If it shipped from the factory with a 1.4 MB drive, it will be labeled "FDHD" or "SuperDrive". Plenty of older SEs were upgraded with the newer drive, though, so that's not a guarantee. The best guarantee is to insert an HD disk you know has nothing important on it, format it, and see what capacity it ends up.
800k drives use Apple's unique read/write mechanism that standard 1.4 MB drives are not capable of reading and writing. This means that a standard PC drive (including USB drives plugged into a Mac,) can not read or write 800k disks. You have to have a real Apple-shipped floppy drive. Apple's 1.4 MB drives can read and write 800k disks.
If it is a 1.4 MB drive, then you can easily write disk images to it from even an OS X computer with a USB floppy drive. (It is apparently possible to write the images to disk from a PC, but I don't know exactly what software would be needed.)
As for newer OSes, Apple makes available System 6.0.8 and 7.0.1 as 1.4 MB disk images, plus 7.5.3 as a multi-part "self mounting disk image". (It doesn't create individual install disks; you have to copy all 19 parts to the target computer, then it mounts them as a single large virtual disk. Although each part does fit on a single 1.4 MB disk.)
If you have an 800k drive, then you will need an older Mac that has an Apple-shipped floppy drive to create 800k disks from the downloadable images. (They have multiple versions of System 6, plus 7.0, as 800k images; and the 7.5.3 multi-part install will work, but you need a way to get the larger-than-800k parts onto the computer.)
The latest System that an SE will run is 7.5.5. You can get there by installing 7.5.3 linked above, then the 7.5.5 Update.
For most programs, you install by just dragging the icon from the floppy to the hard drive, especially programs that were designed to run directly from their floppy. For some program (especially large programs that come on multiple disks, like Microsoft Word,) you do have to run an installer.
One thing to find out is if it has an 800k (Double Sided, Double Density, also incorrectly called 'low density',) floppy drive or a newer 1.4 MB drive (High Density, or "SuperDrive".) If it shipped from the factory with a 1.4 MB drive, it will be labeled "FDHD" or "SuperDrive". Plenty of older SEs were upgraded with the newer drive, though, so that's not a guarantee. The best guarantee is to insert an HD disk you know has nothing important on it, format it, and see what capacity it ends up.
800k drives use Apple's unique read/write mechanism that standard 1.4 MB drives are not capable of reading and writing. This means that a standard PC drive (including USB drives plugged into a Mac,) can not read or write 800k disks. You have to have a real Apple-shipped floppy drive. Apple's 1.4 MB drives can read and write 800k disks.
If it is a 1.4 MB drive, then you can easily write disk images to it from even an OS X computer with a USB floppy drive. (It is apparently possible to write the images to disk from a PC, but I don't know exactly what software would be needed.)
As for newer OSes, Apple makes available System 6.0.8 and 7.0.1 as 1.4 MB disk images, plus 7.5.3 as a multi-part "self mounting disk image". (It doesn't create individual install disks; you have to copy all 19 parts to the target computer, then it mounts them as a single large virtual disk. Although each part does fit on a single 1.4 MB disk.)
If you have an 800k drive, then you will need an older Mac that has an Apple-shipped floppy drive to create 800k disks from the downloadable images. (They have multiple versions of System 6, plus 7.0, as 800k images; and the 7.5.3 multi-part install will work, but you need a way to get the larger-than-800k parts onto the computer.)
The latest System that an SE will run is 7.5.5. You can get there by installing 7.5.3 linked above, then the 7.5.5 Update.