Can't put hay/grass in coop + general chicken related problems

I'm having a few problems and I'm not sure if it's me or the game!

I bought a chicken but I can't put grass or hay in the trough of the coop. It just wont seem to let me! Is there some different action/key I'm meant to be using or is it just not working?

Also my chicken disappeared. I thought it died because I couldn't feed it but then I read that they don't die, they just don't produce as well. I had the coop roller door closed the whole time and have looked all over the farm for it too.

PS where do you find copper bars to build a silo?

 

I didn't get this the first time, too.
You have to put it on the wooden bank at the north wall of the coop.

 

That wooden "bench" looking thing is where you put the feed/hay. As for where your chicken went.... I"m not sure? I'm told even if the door was closed they would still get back inside at night if they were outside. When you first buy a chicken from Marnie you get a baby chick. A little yellow circle. That's the chick & they're a bit tiny. After a few days, it grows into a chicken.
As for copper bars, you have to go mining - there you will find copper ore. There is a furnace you can build. You place in 5 ore and a thing of coal, wait a bit, and wa-lah bar. Or, you could go visit Clint and pay for them.