I understand that Opengl directly cannot load BSP files. How would I go about loading them into my Android game?
Luckily, the BSP file format is well documented (with an overview on wikipedia). While this is great, it's clear from the documentation that you have a good deal of work ahead of you to write a importer for .BSP files.
Your first steps should be getting your file parser working through the lumps and printing out when when it reaches each face/vertex. (Make sure you start testing with a very simple scene).
Next up start loading the vertices into whatever data structures you're using to store meshes. From there you can pick and choose which features the file includes you want to include in your game. Incorporate each feature one at a time, continuing to test along the way.