Thanks for your post! Lucidchart supports importing CSV files to create org charts and ERDs, but this functionality is not available for all types of diagrams. You can also import and export text files to create mind maps. Other file types that Lucidchart imports include: PNG, JPEG, SVG, Visio Stencil files, Visio, Omnigraffle, and Gliffy.
Depending on what type of diagram you're looking to create, follow one of the links above to get started. :) I hope that helps!