Zakbrow

This question is so basic I hate to ask, but everyone was new at some point. I am brand new to installing mods and can't seem to get it to work and can't seem to find a basic tutorial for a first-timer. I click on the mod I want installed, using the NMM option (not manual), and it seems to install NMM, even though I already have it, and it then opens NMM but the mod wasn't installed, or if it was I don't find it anywhere. If I try to download another mod it makes me go through the whole process of downloading NMM again. What am I missing? Any help, even if it's directing me to where I can get the info, is appreciated.