First of all, stick all instances together. It looks like digital standard cell so use them so. Pwell in the same direction, Nwell vice versa.
And if you'll route them just over their area, you can use it as standard cell after that.
I see you built the circuit from library standard cells and then used the auto router. The output is not optimum...
Adjust your floorplan to match the combined size of the cells you are using, plus a bit extra. Your standard cell
will then be the same height as all the library cells, this will be more effective.