Go to store where you can buy some gardening tape and some gardening sticks. I prefer the bamboo sticks if you can find them for cheap. I buy 5 to 7 foot sticks to support branches when the plant starts to thicken out. Line the branch back up with the stalk evenly and wrap it tight. Might be a good idea to maybe pour some rooting solution in there also. After the branch is wrapped up where it broke, I would then support the branch with the stick. Tie it in a couple of spots. Hopefully it isn't too late and your branch survives!