You can use any source you like to export a GEDCOM and then upload it here.
Regardless of the source, you are encouraged to export and upload only a small subset at a time (personally, I think the sweet spot is around 100–150 people). Some programs make this easier than others.
The upload process helps you avoid a lot of tedious re-typing and helps create links between existing profiles and ones you want to add, but you still have to manually review whether there is a match for each person, then add each person one at a time, then go back and clean up each profile one at at time (because the upload doesn't do a great job at extracting info from a database and trying to turn it into a narrative). There is no automatic import.