Custom class hit die in 5E

[Siiepher]

Hello, I was trying to create a custom class in 5E but it wouldn't let me select a hit die. Is this just a feature that I have to buy? Or am I just doing something wrong? Appreciate any help I can get, thanks.

[Edit]
Nevermind, figured out that I have to drop a die onto the hit die area.

[damned]

magnifying glasses
And welcome!