Fitting home made circuit on petrol scooter
In general that's not enough, and there's too many different "right" ways to do it to go into depth here.  Search on "automotive electronics protection circuit" for a start at your reading material.  Then come back and ask about specific issues you have.

You need to protect against voltage spikes up to 60V or so (search on "load dump") and reverse voltage (because at some point you will forget and hook something up backward, not to mention that wiring faults can cause reverse-voltage conditions).