question about building lattice for existed structure

Hi, I'm just new to Materials Studio. I have a question comfused.

Now I have a structure that I know the parameter, however i want to build lattice for this strcuture. How can i do that?

I have tried insert the structure first, then use "build crystal", inputing the known lattice parameter, however the lattice looks strange.

How I can solve the problem?

Thanks!