The Import menu, found on the main menu, contains a few tools that allow you to add layers to your map that were created in another system.  Click any of the options below for more details.

Import SHP file
Import an ESRI Shapefile that was created using ESRI's ArcGIS or some other compatible program.

Import GPX file
Import a GPX file collected by a GPS device.

Import CSV Points
Import a list of point locations from a spreadsheet.

Import CSV Lines
Import a list of simple line segments from a spreadsheet (not common)

Import KML/KMZ file
Import layer(s) from a KML or KMZ file.

Merge Table
Import a CSV file merge its records to existing features based on matching field values

See also Import ESRI Geodatabase

See Export menu also.