Just give it a coat of lemon oil, or similar. I like the Dunlop 65 lemon oil for really dry fretboards. Works really well on new builds where you’re working with freshly sanded and untreated fretboards.
Apply, leave for a minute, then wipe off the excess. Simple as that. No fancy products required. Don’t soak the wood and just leave it. You can always reapply, but I would wait at least a few days to let it properly absorb before thinking of doing it again. I recently completed a laurel fretboard and that needed several applications over the course of the build (three months) to bring it to life.