The Los Angeles Modification made by Hoppah is installed differently compared to majority of modifications.
So, here's a step-by-step tutorial:
1. Open the Los Angeles Modification application.
2. Continue the setup by pressing "OK".
3. Accept the license agreement
4. Your folder pathway should look something like this:
C:\Program Files (x86)\Steam\steamapps\common\EMERGENCY 4 Deluxe
If you do not have EMERGENCY 4 Deluxe and have 911: First Responders instead, then replace the folder pathway to C:\Program Files (x86)\Steam\steamapps\common\911: First Responders.
After that, it should be straight forward from there. If you have any questions, do let me know!