if you want to go on-line directly.. prolly to easyist option.... 'cept you need something to provide an ethernet port for your miggy. A1200/600 a PCMCIA card will do, anything else 'cept A500/CD32 will be able to use a zorro card or pci card.
if you can set up a dial up account, then a cable modem should be even easier. the IP settings should come with the NTL pack. if not, give support a ring and tell them you are configuring a PC manually. don't mention amiga or they'll say that you can't connect to the net with an amiga...