I want to use USE_BED packet in 1.14, but it was removed

well, its has been removed, you can't use it.
sleeping is now part of the entity metadate as part of a new pose field (varint enum) with the values
0: STANDING, 1: FALL_FLYING, 2: SLEEPING, 3: SWIMMING, 4: SPIN_ATTACK, 5: SNEAKING, 6: DYING
so depending on what you want to do, you can just update the metadata of the player.

Thank you

Actually, I didn't understand how do I do it, so I need help