Make a hill

How would I render a hill in playcanvas?

could you be more specific?
One way would be this PlayCanvas Examples

I want to place a hill at the left and right side of the map.

I think you should model the 3d hill and export it to fbx format / or download a hill mesh in fbx format, and add it to the scene in the editor.

For larger maps you can also use a terrain with a heightmap: