How will I get a military ID once I come back into active duty?

You will receive your ID card once you report to your duty station. Make sure you have a photo ID, your Social Security Card and birth certificate, along with the orders they are going to provide you.

You will be issued one after in-processing.

If you have already signed your contract go online on rapids and make an appointment with the closest deer id card center near you. Make sure you bring your contract and ID ect they will tell you what is required.

Same way you get it if you never got out! How do you renew it!

Yes, you will.