To import your .mpp file from MS Project, click on the + icon in the top left corner of the page and then select Create new project. On the project creation page click on Import.
An import window will appear. By default, the project will be given the name of the file that you import from MS Project. If you want it to be different, you can change it in the corresponding field 1. Select the document from your computer or just drag & drop it to the designated area 2, and then click on Import my Project 3.
It may take a little to load your document to the MS Project viewer, especially if you have a big project. When the import process is completed, you will see your .mpp project in GanttPRO simple Gantt chart app.
Note: GanttPRO imports project calendar and task dependencies, and also all the resources assigned to tasks in a .mpp project as virtual resources. Task descriptions, comments, and attachments will not be imported.