Are you having trouble finding a manual?
http://www.replacementdocs.com/download.php?view.372

Sandi1987 wrote:

How to use Health from inventory? Which key? Where can i get ammo?

I notice a trend with a lot of your posts being questions that can easily be found online with a simple Google search. Please be mindful of this.

use next inventory item/previous inventory item to select health
then press the use inventory item key
all those keys can be rebound in the options so the keys i use could be different to the keys you use
ammo is lying around the map sometimes in chests