There are a number of these plugins available for Sketchup and some work better than others. Using a Sketchup STL export plugin, you may also chose to use that format that FreeCAD supports natively. You can filter the file type by selecting the Files of type pull down in the Open or Import dialog and select Collada (*.dae) from the list. Select the File menu and then pick either Open or Import. Providing the p圜ollada module has been installed, you can open or import Collada files just like any other. The direct link to the instructions is - Extra python modules: p圜ollada.

It's a relatively easy task to perform and instructions can be found on the Extra python modules page. To have this functionality in FreeCAD, the user needs to install a Python module for importing and exporting the format. FreeCAD does not natively support the Collada format. From experience, currently the best method to import a file from Sketchup is to use the Collada (*.dae) format.