Now that you have the base and the major supports for your playfield installed you can add the other components. String the elastics, build ramps, and construct tunnels - and whatever other ideas you have. Remember to test often so you can adjust as you go. Watch the video below for some advice on next steps.
And here's some more detail on constructing your side bumpers.
Below is a photo of where my pinball machine is at for this week
Assemble any of the bumpers, tunnels, and/or ramps the ball will interact with.
Assemble the bumbers for around the edges of you playfield.