my son is 18 and worked he made roughly around 12000 how should I prepare his taxes

MY DEPENDENT HAD A JOB

If your dependent has a W-2 for his after-school job, summer job, etc. you do not include the information on your own return. You can still claim your child as a dependent on your own return.  He/she can file his own return for a refund of some of his withheld wages from boxes 2 or 17 (he won’t get back anything for Social Security or Medicare), but MUST indicate on it that he can be claimed as a dependent on someone else’s return.  (Supervise this closely or prepare it for him!)

If your dependent’s earnings were over $400 and were reported on a 1099Misc or 1099NEC then he must file a return and pay self-employment tax for Social Security and Medicare.

You might also want to use free software from the IRS Free File versions:

https://apps.irs.gov/app/freeFile/

If he made $12,000, this is under his standard deduction of $14,600 so unless he had taxes withheld, you do not need to file a return for him.  If he had taxes withheld from his wages, then you would complete a return for him to claim a refund of his taxes.

If he is still a student and you are claiming him as a dependent on your return, then be sure you check the box that says someone else can claim me as a dependent on their return.