OK, so I’ve tested this out and it actually works pretty good.
The manual states that the only supported .csv file is from the Telephone Directory form off of the 3300 (Also note that the .csv must be renamed to MN_Generic.csv in order to work).
To test, I used an older SanDisk Cruzer Micro 2.0 GB USB stick. I had it formatted to FAT32 (Not sure that it matters though). I also tried a USB hard drive which did not work.
It was blank but according to the manual it HAS to be in the x://uc360/backups directory. Once I created that directory, I placed the .csv in there and then off of the UC360 I went to Settings > Advanced > System Settings > Contact Settings. I then check marked the Populate from CSV file: MiVB, MiVO-250 option, and then pressed the Import Contacts from USB option, I then got a Contacts CSV files copied confirmation on the UC360. I then went into the Contacts section on the UC360 and sure enough, all the contacts were in there!
Credit goes to IronGladiator