The national parties have set restrictions about how states select state party chairs election monitors national convention delegates the precincts to target in get-out-the-vote efforts

How states select their own representative.

They select delegates through the Primary election, this is the time they choose their delegates. The people have the chance to express themselves and nominate their delegate. The national party committee helps the states to conduct the nomination.

If you make you mr question more clear I can answer it :)