"Do you put molding paste for texture on a clean canvas and then can I use oil paints on top?" -- Deb
In a word: yes.
In a paragraph: Molding paste contains acrylic polymers, so shouldn't be applied on top of oil paint. But can be applied over acrylic or watercolor paint as well as onto a canvas primed with acrylic primer (not one primed with oil-based primer).
Once dried, it oils can be painted on top. It can also be mixed with acrylic paint, ideal for creating a textured colored ground.
Oils Over Acrylics
How to Apply Acrylic Texture Paste