Start by going to Studio and either create a new template or go into an existing template. Hereafter,
Click on "Rectangle" in your left-hand menu
Go into the right-hand menu under "Edit" and "Transform"
Here you have the option to:
Change the dimensions of the rectangle in the W and H space
Change the color by clicking on the little square at the bottom where you can write your HEX code to get the color just right
When you have customised the background to fit your design you are done - good job 🎉
As it can be easier to see the steps in action to understand the workflow we have made a video where we go through the steps:
A good way to create a more manageable layer overview is to name your layers, go to this article to see how and build the best manageable layer overview 😄
Happy Building 😄