Can't access wifi using my new router

Hi, I'm not very computer literate so please answer in easy to follow instructions. I have a mac that is a year old and been able to access wifi no problem until now. I have had a router put in at home. My partner can access the internet via wifi using his identical mac. I'm stuck to using using ethernet cables as 1. the airport doesn't show up the WLAN network at all on mine.2. I've tried manually joining the WLAN and adding the password. Still nothing.

Whatever I do my lap top just doesn't seem to pick up my home network.It's driving me nuts as I have to sit on the stairs plugged in through a cable whilst hubby taps away in the garden. Have I inadvertantly messed up my setting or something? ta for help x boo

What are the network settings on his Mac as compared to yours?