Dimension Lower Third

Hi, I have to create a custom lower third, everything is going well, but I haven’t been able to figure out how to create custom dimensions, in the sense that in the video I would like to make it small at the bottom left, but by default it gives me full screen, how can I reduce the entire lower? Thanks

My apologies for the delay in my response.

Which application are you using to create the lowerthird background video?
In which of the lowerthird layers of mimoLive would you like to use this video?