This process has been written around the TP-Link range of routers as they are probably the most common budget brand.
The procedure is fairly similar with most other routers but the IP address and the default username and password may differ slightly.
From your computer (or tablet) open your browser (Firefox, Chrome, iExplorer or Safari) and clear the field at the top (where you would normally type or see something like http://...... ) and type in the following; 192.168.1.1
This is the IP address of your router, and if correct, will give you a login screen asking for a username and password.
For the majority of the TP-Link routers the default username and password is admin and admin (both lowercase) and this hopefully will display the router’s control panel.
Depending on the age of your router you will see a menu on the left with a fairly self explanatory set of options that will let you navigate to the screen where you can change the Wifi passcode.
You may need to re-enter the admin password before you change the current WiFi passcode and I then prefer to simply change a couple of characters which helps me keep within the rules regarding acceptable characters and password length.
Good luck and please email us if you get stuck