ModuleNotFoundError: No module named 'cv2'

[FilippoRomeo]

After installing OpenCV
** Install opencv-4.5.0 successfully ** Bye :)
It says

python3
Python 3.6.9 (default, Jan 26 2021, 15:33:00) 
[GCC 8.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import cv2
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'cv2'

How to solve this?