If Paint will open from Help & Support, then it clearly can be found on the computer. Perhaps you somehow managed to delete or move its Start Menu shortcut? I can't imagine how this could be done accidentally, but stranger things have happened.
In Windows Explorer, browse to the C:\WIndows\System32 folder, right-click on the file "MSPaint.exe" and select "Create shortcut." You'll be told that you can't create a shortcut in that location, and offered a choice of placing it on your desktop. Once the new shortcut has been created, you can move it back to the C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Accessories folder, where it normally resides.