May 26, 2016, 13:0605/26/16
Greetings m'lord!
A small red button with a cross in it should give that opportunity.
However, I believe you can only do such thing in the first 30 seconds you started the upgrade. If this time expires, you might need to boost the construction in order to make another one.
Another option would be purchasing Craftsmen who would love to help you out! They're found in certain offers and you can purchase them with Sapphires. The first one is 1500 Sapphires.
Hope this helped you out!