There is a great deal unstated in your post, perhaps because you have already posted it somewhere else, or because you believe that we shall understand the unstated, or because you are not aware of what is needed to get access to the Web.

Have you an account with an ISP? For dial-up, ADSL or something else? What is the DSL 'box'? A telephone modem? An ADSL modem/router, a telephone line filter or something else? What OS is on your iMac? Which iMac is it? Are the passwords at the hardware level (eg on the HDD), in software (as in At Ease) or in the System software?

Some background will help us to help you.

de

Edit: I see that Anonymous Freak has already given you info. about your options.