Paul, how do you mean?
I'm not at all familiar with the Mac or what software comes bundled with the O/S, but I assume that you already have a web browser and e-mail program with it?
Somewhere in those packages you should find an option to set up a new dial-up connection. It might be named "Add connection" or "New account" or something like that.
It's then just a matter of entering all the relevant configuration data, which your ISP should provide: Telephone number, user name and password, server addresses for incoming and outgoing e-mail, etc.
oh, yes and you'd be proud to know I took your advice from the electronics info thread and rewired a plug. I had a friend talk me through it over the phone. The color of the wires were tricky.
With an American cord into a British plug, you should have ended up with green on the earth (ground) pin at the top, white to the neutral on the left, and black to the fuse on the right.
Anything else I should be aware of?
So long as you got the connections right and the cord terminated and secured properly, you should be fine. What size fuse did you use in the plug?