|Basically you will need to login to the router's admin/setup page(s) and enable wifi. By default it is is "usually" switched off when you receive the router.|
Each computer/ipad will need to know the SSID for the router (it's name which it broadcasts/radiates) in order to connect to it.
Ideally - and highly encouraged - you use an encrypted connection too; which means each device must provide the password/access key in order to connect to the router. That password is already provided within the wifi section of setup, and you may also find on a card in the box the router came in (happens occasionally). Make a note of it regardless. (There are other levels of access control too; details are in the user manual.)
There is a little more to do but we will need the router model etc. in order to provide full "how to advice". It will all be in the manual for the router; which you may or may not have?
Post back with router details for more help...