Hey there @MegaPony128, first of all welcome to the site!

To import items to the adventure from your main inventory, first make sure the pet that you want to give items to is on your adventure squad. If they're not, they can be added from the adventure home page.

Then make sure you aren't currently in an adventure. Any ongoing adventure can be ended by taking your pet back to the Entrance Gate and clicking Finish Adventure.

Next on the Home page, find the pet on your list of adventurers and you should see an "Equip" button. Click this and you'll be taken to a page where you can equip them with items and currency from your main inventory.

Keep in mind that only some items can be equipped, such as adventure potions, attack scrolls, and...um...I'm drawing a blank but I'm pretty sure there's something else LOL. I'll let you know if I remember xD

Please let us know if you have further questions! We'll be happy to help :)