Belkin Router

Excuse me if this thread is in the incorrect place but I am at my wits end!

I had to use a friends router when installing it to allow wireless network on my laptop but now I’ve bought my own router. I swopped all the connections round but now the friggin’ internet won’t work if I add security with the wireless connection whereas I can still use the internet on the laptop if the connection is unsecured. Pleeeeeeease could someone enlighten me on why this is happening, it used to work with a secure connection.