HSFX does not add new campaigns to stock ones. It provides, so to speak, "materiel" to build them: planes and maps. You need to download new campaigns from sites like
M4T and
A&A. You have two choices: one is to download campaigns for stock game (perfectly compatible with HSFX), enjoying HSFX sounds, 3D models, etc. Second is to download campaigns specific for HSFX (like static ones including new maps and planes) and for Asura's DGen_MOD which allows same goods in dynamic campaigns.
I hope to have been clear enough,
GB