You need some hardware and software. The hardware depends on what type of broadband connection you have.
A modem if you have a dial-up ISP, or a router if you have a broadband connection. If you have a router, you need a PCMCIA card for a deskptop amiga or ethernet card for towered amiga.
You need an IP stack. Miami cannot be bought anymore so you need another: There is one on the OS 3.9 (3.5?) CD, Genesis IIRC.
Again, on the OS3.9 CD, there is a browser (Voyager?) available. Or, you can get demo versions of IBrowse or Aweb. IBrowse is still being developed, is currently at stage 2.4 but V3 will come, but not any time soon. You will need to pay for it but it's worth it.
You need an email program to do email, IRC program (Jebberwocky on Aminet is good, & free) to connect to your MSN & Yahoo friends.
Anything else and we'd need to know what hardware you've got and what your needs are
