Hi Fernando thank you for posting in the Lucid community! Our sincere apologies for the delayed response on this thread - I wanted to follow up in case this answer may still be useful to you and to provide a solution for other users who see this thread in the future. 

You first will want to ensure the process diagram and blueprints have been imported into a Lucidchart document. Once your work is in Lucidchart you can utilize the layers feature to move the additional process diagram onto an additional layer to place within your blueprint.

Take a look at our Add Layers to a Diagram article in the Lucidchart Help Center for more information!