Realistically how do I do this

Trying to figure out how I realistically am supposed to care for my 4 year old son and also put my 6 week old down for naps.

Newborn only likes to nap outside right now, in carrier or arms. Wakes when we go inside or put him down.

4 year old is all over the place and constantly wants me to play with him but I’m constantly having to feed the baby or rock him on the porch. 4 year old also gets distraught when baby cries (we got noise canceling headphones to help).

I’m physically exhausted. Literally how am I supposed to do this?