For anyone who might want to learn from this in future, I think you either need to root it with a method like this:
Root Samsung Galaxy Spica i5700 With LeshaK’s Kernel
and then install a program like "wireless tether" or "Barnacle Wifi Tether" off the market, or just update the firmware to 2.2 or something:
Android 2.2.3 Froyo (Mod+X => SpicagenMod BETA5) ? Samsung GALAXY SPICA I5700 | SUCKUP.de
I dunno if you need to root it first o.O
I also don't know if you have to root it before updating the firmware... probs not but I dunno!
I'll decide on something then do it lol