Ask your patient to lie in a supine lying position.
1.The examiner then brings the affected leg's hip and knee into 90 degrees of flexion.

2. The examiner then abducts the hip and externally rotates it so that the patient’s tested leg foot rests on the opposite leg distal thigh. This is the Faber position, or figure 4-position. That's why this test is also known as the figure four test.
3. The examiner then places one hand on the opposite ASIS to stabilize the pelvis and for more information you can visit - https://physio-study.com/faber-test/