Don't wish to dwell too long on this and waste space, but can anyone provide some basic help. Please.

This machine is a newish Apple MacBook, connected to a Telstra Bigpond 7.2 Home Network Gateway modem, linked via ethernet cable. It works. Don't wish to fiddle with this.

The other laptop, an Apple iBook G4, is in perfect working order, but does not have the grunt nor inclination to handle lots of bulk raw images. Hence the laptop update. The other laptop, the Dell, is a disgrace to itself and should not be seen in public. A solidly built, attractive package that promises all, but delivers zilch. Farther more, it has proved impossible to obtain replacement valves.

What I want to do is fire up the older Apple laptop for my wife - wirelessly - without changing settings on the main unit. Is this possible?

Kindly treat me as a computer illiterate. Ta. Thanks in advance.