Assuming you've already got the network set-up (the 3 PC's share an internet connection and files?) then all you need do is share the printer on the PC to which it is physically attached (control panel, printers, right click on the printer to be shared and select sharing, then share this printer, give it a name and OK). On the other PC's you'll need to add this new network printer (control panel, printers, add a printer and follow wizard but making sure you add 'a network printer or printer attached to another computer' option. If this works OK you should be able to select the networked printer from any application on the other 2 PC's.
If your running XP on all 3 it should be very easy to do following the above advice.
I had no problems networking a printer between XP and XP but networking XP and ME was a little more involved. I presume it would also be the case for 98. Basically I had to install the drivers on the ME PC first which wasn't straightforward.
don't think you can share printer without networking the three PC's together. Sounds like you haven't done this and don't have any wireless networking hardware other than the three wireless cards that are in the three PC's. Check out this, it may help click here
If you're running XP you may need to do nothing at all - last time I added a PC, two "Auto" printers appeared in the Printers folder in Control Panel after half a minute or so. Not sure this works with all printers, but did with my HP959C & Samsung laser. If not, m235374's method above is the way to do it.
OK, so you have a wireless router on the main PC and have a network established. In that case I think all you need to do is run the wireless network set-up wizard on the other two PC's to connect to it. Have a look at this article click here;en-us;314897&spid=1173&sid=1248