Why can't I install Mods on Minecraft Pc?

So I'm guessing you are using forge for your mods. Download it and install to minecraft by double clicking it. If the mods folder does not appear. Make your own file and then place the mods and it should work.

1. See if your installer and adobe flash player is working,
2. If it is, go to the mincraft mod launcher
3. If it still works, then there might be something blocking it launching
4. If there's nothing blocking(and I mean nothing), restart the computer
5. If that doesn't work then someone might be hacking your computer,
6. If none work, then re install it

Because its not there as standard. You need to add it yourself.