How can I centre a container? (GenerateBlocks)

Hi, I am hoping someone can help me with this.

I am using GeneratePress (Pro) and GenerateBlocks (free).

I have my home page set to full width / no sidebar.

But, for some reason I can’t get the content in my container to move into the centre.

I have it set to 80% width, and I just want to move it into the middle.

What am I supposed to do, I feel like this is going to be something super simple, but I can’t figure it out.

Thank you in advance,
M.

P.S.

It’s a private site for a client, so I can’t give access. But, this is just on a normal page, with no CSS and no plugins (other than GenerateBlocks and GeneratePress Pro).