Try to reinstall it.
Or check out the minimum requirements
The OS should be Win 7 64, CPU Core i3-3250 3.5GHz or Intel Pentium G4560 3.5GHz / AMD FX-4350 4.2GHz, R.A.M -6 GB, GPU: GeForce GTX 660 2GB GTX 1050 2GB / AMD Radeon HD 7850 2GB and HDD:68 GB. I know some of my friends
and they are also trying to add it into Fullscreen but they had found out the minimum requirements was not fulfilling. As they had again reinstalled it and then it works.