First navigate to the making a yarrly page by opening the app from a cold start, tapping 'new' in the wheel menu or 'remix' in the wheel manu if you want to add a Yarrly to that chain.
Then tap on the top and bottom default images (or remix images) to bring up the addinf a photo menu. Tapping will show a camera (to take a photo) and a gallery icon (to used a photo in your gallery). Navigate through these to import a picture into these two spaces. Only when both pictures have been filled can you tap the wheel to make your Yarrly.
If you want to rotate the images the double tap them.
If you want to zoom in the make a pinching action with your fingers (like if you were using your finger and thumb to impersonate a parrot talking).
If you want to swap the images from to to bottom or copy them so you have both images the same then long swipe from top to bottom or visa versa then select copy or swap.
Add text to the top and bottom images if you want by tapping in the text field and typing. Wizz bang you've now made a Yarrly.
Tap the wheel to finish everything off by hitting 'create'.
Once you have created your Yarrly you automatically have the option to share it.