Garmin Connect's own app-settings screen crashes side-loaded apps like BulkForged, so entering a pairing code happens entirely on the watch instead.
Eight digits, entered one at a time, with the active digit highlighted and underlined.

A rejected or unreachable code shows an inline error so you can retry without leaving the screen. Once it succeeds, the watch gets its own revocable token — there's no shared secret to leak, and re-pairing later never touches anything you've already logged.
Related: "My Garmin watch stopped syncing — is BulkForged broken?", "Account & watch".