Many of the processes and laws that govern voting, the options voters have, and the deadlines for various stages of the process, vary from state to state.
It is essential that voters inform themselves of how elections work in the state where they are registered. This website allows you to find the election website for your state: https://www.usa.gov/election-office.
As for voter registration, please note that (with the exception of Wyoming and North Dakota) you can utilize the National Voter Registration Form (find it here in English and in other languages). You can download copies of the form, and instructions on using it.