Hearthkyn Theyn in the box art orange armour.

Prime

1. Prime with a light primer. Here I have used Desert Sand Primer . Any light primer will work for this step. I have airbrushed this on, with a tiny bit of flow improver and a little thinner. Allow at least 10 minutes for the primer to dry.
2. I have then used liquitex Titanium White ink to bring the base coat up to a reasonable white. If you can get a white primer, use that for both step 1 and 2

At this point, if you have the time. Leave to dry/cure for 24 hours. It's not entirely necessary, but AK recommend 24 hours for the primer to dry fully.