How do stealth aircraft get ATC?
The concept of ATC is based on primary radar targets, secondary radar targets and radio communication being used to determine the position of aircraft and establish separation.

The concept of stealth aircraft is to reduce production of primary radar targets and being able to turn off transponders to disable secondary radar targets being visible. Stealth aircraft also do not communicate on frequencies during tactical missions, they are designed and meant to reduce radio emission to enable the stealth features.

If they are not on a tactical mission and stealth is not required, they will simply turn on their transponders and communicate with ATC on the required frequencies.