Now, there's only one more thing to do before you can play your map and test it out. In order for players (and bots) to spawn in your level, you have to have 1 or more player starts. Fortunately, these are quite simple to add. Simply right-click on the floor where you want your player start to go, then choose "Add Player Start Here". Rotate and fine-tune the positioning as you see fit.

Now all you have to do is hit the Rebuild All button (1 in the diagram) and your map's ready for play! Be sure to save your map after rebuilding to keep all the work you've done (and just in case something happens to Unreal Ed). After saving, click on the "Play Map!" button (2 in the diagram) to try out your new map. Happy map building!