It was my first time voting for the next president of the United States of America and also I am Christian. So when I was 18 I was still a democrat then change my mind to a republican, but sometime on the election day I will sometime choose for both republican and democrat but sometimes not all time. Then my mom was a little bit upset and say you if you want to change into a republican you need to go State house and ask them to change it for you? I was 19 years old and I believe that. Is that true that I need go to the State House to change my democrat to a republican registration, or was it just a my mom emotion saying whatever was in her heart?

Your vote is private, and no one will know who you voted for but you. In some states, you may need to register with a party to vote in that parties primary (which you can do with your state board of elections), but in a general election, you may vote for whomever you want, regardless of your party affiliation.

Agree, no one goes to the state house and declares what party they are. In some states you wlll as noted, have to register where you vote as to what party you will be listed as.
This is for use when you vote in primary elections. But you are free to vote for any or a mix, I never vote straight party ever and vote for the best person.

Why does you being a Christian matter?

It would be very unusual for you to have to go to the Statehouse to change your registration. Most counties or parishes have an Elections office that handles those things. Some places call it a Commission office while others call it a Board. Your current voter registration card should have a way to contact them on it.

I bet your county board of elections has a site that you could change party affiliation on line or at least down load a form to mail in .

Because Christians should not give a vote for a candidate that supports gay marriage, abortion.. etc, etc..

Why do you think that not all, but most gays, atheist and people who are for abortion vote democrat?. simply because that is the party that supports such ideas.

Like I said... this is very important IF YOU ARE A CHRISTIAN... if you're not, then this things are not of importance and you should vote mainly on political reasoning.