How to Create a Template
You would create a template the same way you would create a moodboard.
Many designers create a new project and call it templates. You can then create each of your template boards within that project. It's entirely up to you.
To create a new template, you will start by creating a new moodboard design and entering the editor.
You can add any images you would like to your template including your Logo, lines, arrows, etc. This would have already been uploaded to your library. Here is an example
You can also add in editable information such as the Project name and Room. This information can always be edited whenever you load the template to match the current project you are working on.
Once you are satisfied with the template, you can go ahead and save it by selecting "Templates" in the upper right, then select "Save as Template"
Give your template a name and save.
Now you can load that template into any other moodboard. Once you are in the editor, go back to "Templates", select the name of the template you want and it will load everything that was saved in the template. You can then make any edits you please and continue with your design.