For Turn WiFi ON/OFF for your computer.
Click on the Windows Start button and then click on the Settings icon in the little menu that appears.
On the Settings screen, click on Network & Internet .
On the next screen, click on the WiFi option in the sidebar menu and then toggle ON...
If any issue let me know which operating system you have for your computer so i can advised you accordinly. some desktop doen't have wireless adaptor so that might be reason as well for not detecting wireless network.
Turing on /off wireless from router,see below link
How to Connect to Your Wi-Fi network, see below link.
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