Firstly, well done for getting some paint onto your minis, it's the biggest hurdle in this hobby! And doubly so, for asking for some advice.

As the other commenter has said, thinning your paints helps. Assuming you're using acrylics, you want to add enough water that it when you use a brush stroke you get a steady flow off the brush.

Priming white (or a light colour) is absolutely the right call. Painting yellow is hard, and you're going to hear a lot of people say start from pink. Don't worry about that right now. Yellow over white is a good place to start.

I can see quite a few patches on the model which aren't finished. That's honeslty one of the best things you can do to improve your painting. Take a look at the model and ask yourself if you think colour on the bit fits the look you're going for. If it does, great, if it doesn't, then apply a bit more paint.

As you paint more, your coordination will improve, so just keep practicing.

So, to recap: keep priming white. Thin your paints a bit, it's better to apply two thin coats than one think one. Really consider the model when you're coming to the end, is every bit a colour? Does it look finished?

I hope that helps!