Schematic on Claim

To have a schematic pasted on a plot when the plot is claimed you need to:

Build in a plot. If you want an external schematic, then use WorldEdit to paste it in the plot (Tutorial)
Use /plot schematic save to save the schematic. You can find a list of saved schematics by using /plot schematic list

Now you have a working schematic file. To have it paste on claim you'll need to configure your worlds.yml, here is a simple snippet explaining how to do that worlds.yml.

# The following is a slice from the plotworld settings, change this for each plotworld
schematic:
    # File name (without .schematic)
        file: 'schematic_name' 
        # If you want it on claim
        on_claim: true`

and in settings.yml, add/update the following:

# Schematic Settings
schematics:
  # Whether schematic based generation should paste schematic on top of plots, or from Y=1
  paste-on-top: false

You can use the same schematic for more than one plotworld.

Note: If you activated the "specify_on_claim" option in the world.yml the user can define a plot-schematic with the claim-command: https://github.com/IntellectualSites/PlotSquared/wiki/Commands#claim