OK I got a bug up my butt and thought it would be cool to separate my operating system from my flight sim and clod

so I put windows on a new 250Gb ssd. and have a Samsung evo 500 for steam and games , the evo 500 is blank. so docent steam need certain folders that the operating system has "program files 86, " my documents act

I set steam to download to my evo 500 and the install button stays greyed out ?