Owls spawn naturally above grass blocks, dirt, coarse dirt, snow blocks or podzol in forests, taigas, groves, old growth taigas, and snowy taigas, along with all variants of these biomes (with the exception of flower forests), in flocks of 4.

For starters, you can't tame the owl. However, if you give it an item it will prompt you with a choice of any player outside of a 24 block radius to send it to. Once the owl has delivered it's item it will return to the block of origin. The owl locks onto the player that last gave it an item. It follows the player from up to 64 blocks away even if it can't see them.

The Owl currently drops 0–2 owl feathers. These new feathers function exactly the same as normal feathers!

The Owl can hold virtually any item handed to it and will deliver it on command.

In short you can't. However, if you want to deliver more than one item to a player utilizing, a bundle or a shulker box will definity do the trick.

If the owl is displaying as a sunflower, it means that the resourcepack is not enabled. The resource and the datapack are the same .zip so be sure to put the datapack in your resourcepacks folder aswell. If you're on forge it may be because your mod resources are below Minecraft in the resourcepacks list.

If you have any unanswered questions feel free to have a look at the owl's wiki page. Owl Wiki