How to install vst instruments

i have a problem,
i found some websites that you can download some free vst instruments, and when i download the file and put it in the plugins folder it’s not working, i tried to put it in almost all the folders inside the cubase folder and i have no idea what to do, (i also put a vst plugins path to one of the folders and it still not working)

does someone know how to install it?

and another quest, does someone have a good free vst instrument for rock drums?

Thanks for the help,