cant get this to install in my subfolder. any help?
If you intend to install GRAV in a subfolder you must then also edit the .htaccess to point to your subfolder. Further info is also written in this .htaccess file located in the root folder of GRAV.
Not necessarily 
More often than not you don’t need to touch the .htaccess at all. Most hosting situations will not require this. If you are running Apache, and .htaccess is allowed and is being processed, it should just work no matter the directory you extract it into as long as that is under your apache web root.
However, be careful to extract the zip file and rename the resulting folder because if you just extract and copy the files, you will undoubtedly not select and drag important hidden files (like .htaccess)