A little tip for artists:
If you buy canvas that comes already primed or with "Gesso" as it is called applied, it is always a good idea to add one or two more coats of Gesso yourself at home before you paint.
Gesso is essentially a primer for acrylic paints and it will prevent them from soaking into your surface (in this case canvas) as well as provide some texture/tooth for the paint to pick up on.
Even though these two canvases are for my niece and nephews kid art show projects I still applied Gesso so that they get easier paint coverage.
It's easy to apply with a larger brush and there is really no wrong or right way to apply it. If you apply a few coats, you can also lightly sand them in between (must be fully dry first) to smooth out the surface even more - it is completely up to you and your preference.
It does add a bit of time onto the start of a project to apply it and allow for it to completely dry or cure.
But it will be so worth the added step.