Manual Install?

I want to install the mod (it looks fantastic) and so I downloaded the 7z archive and the installer. However, when I run the installer it starts extracting the archive and all to my default drive (D:) but I barely have any space on D: because it’s a very small partition I only use to run Windows. So there is no room for a huge archive to be extracted to D:, even temporarily. So I went into the 7z archive in WinRAR and I wonder how I might go about installing it that way? I see no EXEs or anything so is it really all in the archive? I just need some kind of way to install it on my storage drive myself.

Go here: C:\Program Files (x86)\Steam\steamapps\sourcemods
create a folder called BMS then put all of the files inside the BMS folder from the .7z then restart steam, Black Mesa should appear in your library.

Founded in 2004, Leakfree.org became one of the first online communities dedicated to Valve’s Source engine development. It is more famously known for the formation of Black Mesa: Source under the 'Leakfree Modification Team' handle in September 2004.