I am in the process of painting my 120mm Waffen SS officer and would like to know how to paint the leather holster and the belt.So,with this in mind I would like to know using Jo sonya acrylic paints what are,1.the colors needed to paint leather and 2.Are there how to videos on painting leather?
Thank you.

Lot's of videos on Youtube. Here's one.
https://www.youtube.com/watch?v=7Reb894lDc0

Don't know Jo Sonya acryllics, so I can't say which specific Sonya colors to use.

I recently painted gunholster and leather boots on a 120mm WW2 german soldier. Kept it very simple. Painted flat black, drybrushed with an orange brown color and rubed the painted(Dry) parts with my fingers, to give it a little shine. Very old school with drybrushing,but I like the result.

I like this technique:

http://www.planetfigure.com/pages/Painting-Leather-Boots/

i work with oils usually but i think with acrylics you use the same colors just with different tecnique

Acrylic base, depending on what kind of leather it is, dark, clear, reddish, etc .... I choose a medium/dark shade.

Then with oils i prepare a palette on a plate in this sequence:
Cassel earth
Burnt Umber
Raw Siena
Napoli Bright yellow
white Titanium

i mix the colors in the same sequence

Personaly i use oils from Talens Rembrandt but the colors name are standard even if sometime the shade is little bit different between manufacturer