Usually there is a network or wifi icon (a little computer screen thingy) in the taskbar at the lowwer right of the screen. if you right click on it a menu opens up where you can connect to network or diagnose or repair a problem. If you are using a cable modem to get your internet and have a router for your wifi signal it sometimes helps to unplug both of them for a few minutes and then plug them in again so everything resets.