To scatter objects on a surface you first need to have an emitter selected. Then, click the '+' icon in the top-right of the addon panel. This will add a new scatter system using the selected emitter object.

Now, go to the "Instances" category. Here you can choose which instances to scatter on the surface. You can use the 'Type' menu to switch between scattering a single object and a collection. To control your scattering, go to the "Scattering" category. Here you can control the density and seed. You can also enable the option called "Limit Self-Collision". This will show you a new value that you can change. This will control the minimum distance between each scattered object. From here, you can play around with all the different categories to get the results you want. We'll go into details on each of these on the following pages.