I'd like to mirror a triangular prism I made. However, whenever I select it I am only able to select the faces or sides.
Is there a way to select the whole 3D object to move or mirror it?
Yes, there is a "select" tool in the toolbar next to "make". You can use select filters to select components, bodies and faces.
Selecting the body in the browser will select the entire body. Clicking on the body in the viewer will only get you faces or edges.
A long click (click and hold) on the model will give you options on what to select. You can choose a face or body under "Depth" or choose a body or feature under "Parents."
In the top left of your workspace (still inside the editor) you will have a dropdown, in that dropdown there is a folder called bodies, open that and select the body you want. You can then move the selected body.