If I rear-ended a car but got scared so walked away from the scene and now go to the police station, will I be arrested or just issued citations to appear in court?

Leaving a scene is an offense.  However, if you are up front about accepting responsibility, law enforcement tends to be more lenient.  Usually this type of offense results in a citation with a requirement to appear in court.... but considering that you did leave the scene, they could require you to post a bond to insure your appearance at court. 
This is not an easy situation to predict because much of what could happen depends on the personalities and procedures of the law enforcement agency handling the investigation. However, if you have a minimal history, you are not looking at major, over the top punishment.  This is a "pay some restitution for a dismissal" type case.  You just need to find a defense attorney that will help walk you through the process to get the dismissal.  You are not required to hire an attorney, but considering this is your first offense, invest in the funds to obtain one.  Many people show up to court, sign what they are told to sign, and then end up with a conviction on their record without ever really understanding what they just pled to.  They are just happy to be done, not realizing the long term consequences on their jobs, their insurance, or any other areas their lives.  Take an attorney so that you know what you are signing and what the consquences of any documents are.