Confused on how to password protect FileMaker Pro v13 file
I've recently upgraded my FMP from v8.0 to v13. I built a new db by trying to drag & drop a .numbers file into FMP and it didn't work so I exported it as a .xlsx file from Numbers and got it into a .fmp12
Now I'd like to Password protect that simple database. I'm simply wanting to put a password on that sole file. Since I'm new, the permissions and rights and administrator, etc is confusing. How do I lock up that self contained little file so only I can open it and search the contents for data. I share that file across all my Mac devices, iMac, MacBook Air, iPad and iPhone via Dropbox.
Would appreciate a couple pointers.