I'm getting broadband soon (ADSL) and I need to know some things. Firstly, I'll have the main computer (which is downstairs) hooked up to the ADSL modem, then I wanted to get two wireless connections (that will go upstairs), they need to connect to a Dell laptop and an iMac. What things do I need to know? Or how would I connect them all up? Any security measures I should take?

Any help would be appreciated.