How do stealth aircraft get ATC? I believe that all aircraft must be controlled under ATC's instructions to fly safely especially when take-off and landing. And, most ATC instructions are conducted by ground radar which controllers use.

But I know that the stealth aircraft (including B-2, F-22 etc.) aren't captured on radar display owing to their stealth ability. If so, how does a controller give instructions like radar vectors to stealth aircraft?

I know that there's are primary and secondary target when using radar, and the controller must use primary target to vector aircraft. I guess stealth aircraft can be captured by secondary radar but not primary target.
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.