I'm doing the mission called Old Guns. I'm at the part when you have to build and assign artillery at the castle. I already put 2 artillery pieces in the castle but I still can't progress. I tried talking to Ronnie Shaw after and she says, "But what are you waiting for? Get that artillery settled". What is it that I didn't do or did wrong? When I went back in the workshop menu, it says that I have to use artillery smoke grenades to call in artillery strikes on your enemies. I have no idea what that means. Please help. Thanks.