If you aren't using the IDE and you want to manually install a BSP archive, we recommend that you create a default directory with the same name as your BSP and unzip the archive from there:
For example:
mkdir /home/joe/bspname
cd /home/joe/bspname unzip bspname.zip
Each BSP is rooted in whatever directory you copy it to. If you type make within this directory, you'll generate all of the buildable entities within that BSP no matter where you move the directory.
When you build a BSP, everything it needs, aside from standard system headers, is pulled in from within its own directory. Nothing that's built is installed outside of the BSP's directory. The makefiles shipped with the BSPs copy the contents of the prebuilt directory into the install directory. The binaries are built from the source using include files and link libraries in the install directory.