Usually, you only claim a credit in the case of a full year resident of one state paying tax in a non resident state.
It's more complicated, in your situation, because you were a part year resident of both states. Rather than claiming a credit, on your CA return, I recommend, you claim it on your UT return, because you were a UT resident at the end of the year. This means you should prepare your CA return first. In both state interviews you will be asked to allocate the capital gain as that state income or not that state income. You will indicate, on the CA return that it is CA source income. You will indicate on the UT return that it is UT source income. In the UT software, you will be asked if there was any income subject to double taxation (this is usually in the credits section) That's where the credit will be initiated.
I am not specifically familiar with either CA or UT software and am describing, generically, how it's usually done.
