Freddynyc

Hey there.
If you notice the way how those callout plugins are placed in the directories when you downloaded them, just place them according to what you see.
E.g.
CallOutsV
- LSPDFR folder
- Plugins folder
 
You will see both folders in your GTA V main directory as well. Just copy both folders into your main directory. Once you get on duty, the plugin will load with a popup in a rectangular box above your map.
As for vehicles, there are two types namely an "Addon" and a "Replace". Exactly what it means, an Addon is an add-on while a replace is replacing the vehicle as one of your current GTAV vehicle.
In the case of "Addon" vehicles, you require a modified "gameconfig.xml" file which allows custom vehicles as well as several things in order to get it to work!