How do you use V-Union cards in TGC Live?

Apologies if this is a really dumb question, I just started getting into playing the tgc at all and I'd like to use these V-Union Morpeko cards I got a while ago. The v-union description just says "combine 4 different v-union cards from your discard pile and put them in on your bench," but im not clear what that's supposed to mean. I tried a test game but it wouldn't let me do anything with the v-union cards in my hand, even when i got all of them in my discard pile like it suggested. What am I missing? Thanks in advance to anyone who can help me out. 🌟