Hello Nicolás thanks for posting in the Community! You should able to simply click anywhere in your diagram (after selecting everything), then drag your mouse to reposition it entirely. Are you specifically having trouble with this?

Additionally, here two more ways to go about this... if you would like to make space you can either 

1. drag and drop a shape to a new section of your document that is grayed and shaded out. This will then cause Lucidchart to create additional white space for editing. For example if I wanted more space above my diagram I would drop a shape in this section right here...
2. Another way to do this would be through grouping. To do this click ctrl+A then click "Arrange">"Group" on the top banner. This will make it so that all your shapes are grouped together so just with one click and drag you will be able to move your entire diagram to wherever you want on your document. After you do this you can ungroup these shapes by clicking "Arrange">"ungroup".

Please let me know if you need additional clarification on this!