Make sure you set 2000 as action id - If you set 2000, whenever someone click on the chest, they will always recieve the item.
Then set a completely random unique ID that hasn't been used before.
After that you should click on one of those black boxes below "Contents" that you can find inside the chest, add a backpack there then right click on the backpack and select Edit, now you can add all the stuff inside that bag, and the player will recieve a bag with items in it when clicking on the chest.
I believe there are a lot of tutorials about how to make quests if you look through the forum, but I covered up the most basic stuff for you here.
Good luck