You'll meet with a recruiter. You'll take the ASVAB. You'll go through MEPS. You'll sign your contract. You'll train and obtain your MOS.
If you're considering a career in the CA ARNG, keep this in mind. You may not get the job you want. You may need to re-class to a different MOS if your position disappears, or the needs of the Army changes. Siemper Gumby - always flexible. You just need to have a sense of humor at times and talk to your NCOs. They are some of the best people I've ever known.