Can I use espresso in a French press?

Yes, you can, but as the other responder wrote, the filters in a French press are coarser than the filters in an espresso machine, so the resulting coffee will contain some coffee ground residue, but the flavor should be fine. Generally you need a coarser grind for a French press. The same type of grind that you would use in a standard drip coffeemaker would work well in a French press.