In general, Garmin Connect is for Garmin devices. Can you zip and attach an .ifit.tcx file so we can take a look?
Zip the file, then in a reply post Insert >> Image/video/file >> click Upload >> browse for file >> OK.
Or upload the fit file to a file sharing service, such as OneDrive, Google Drive, Dropbox, etc., make the file public, then paste a link to the file in your post.
Without paying for the software, there is only so much you can do. That might be what's preventing you from doing this. What I did was change the activity type to walking, then export the file as a .fit file. The software took care of the distance.
