Get yourself a copy of the how to paint manual from games workshop stores. Firstly, learn how to use shades and dry brushing. It will help you enormously and will quickly help you paint better models. Also, thin down your paints. 2 coats is always better than one thick one. From the photo, it looks like you've used one thick coat. This obscures fine details and wrecks the base coat - which has a knock on effect for the rest of your painting