If you want to import your FitBit Aria scale measurements to Garmin, you can use free online service http://www.fitdatasync.com. Once you registered and linked it to FitBit and Garmin, it will automatically import weight to Garmin and activities from Garmin to FitBit.
Does anybody know of any way to sync more than just weight into Garmin Connect? I like my Fitbit Aria scale. I got it to replace the Tanita BC-100 that died (I always hated how difficult it was to access the data anyway - into your watch, sync the watch--- too many steps just to see what you weigh.)
If I'd known there was really no option to see this data in Garmin, I might have rethought this purchase. I'd even be happy if Garmin would just let me manually enter more than the weight. I think it's total nonsense you can't manually enter data.