This is how i activated windows a couple years ago so theres no guarantee that it will still work. It's also probaly not 100% legal.

step by step:

step 1 : open the command prompt as an administrator

step 2 : use slmgr /ipk to install one of the license key at the bottom of the page ("slmgr /ipk *key here*")

step 3 : use slmgr /skms to set a kms server, i would use "kms8.msguides.com" (i have my own server but it is not stable) but there are other options ("slmgr /skms kms8.msguides.com")

step 4 : finally use slmgr /ato to activate ("slmgr /ato")

You should see a pop-up windows that says "product activated successfully" somewhere on it. If you dont see it or it says something else then repeat step 4, the server was probably busy.
_{note: remove the quotes from the sample commands!}

windows license keys:

home: TX9XD-98N7V-6WMQ6-BX7FG-H8Q99
professional: W269N-WFGWX-YVC9B-4J6C9-T83GX
enterprise: NPPR9-FWDCX-D2C8J-H872K-2YT43
_{(if they dont work message me or look online)}