To install as_endore simply unzip to anywhere on system, open the file inside there will be a series of folders.
Move overviews to c:/sierra/half-life/cstrike. Click yes to over right
Move gfx/Podbot and Maps to same place.
Move brick.wad to c:/sierra/half-life/cstrike
Other files like this and the readme.txt are just for you to read if you wish they are not needed to play this map.

Have fun!