1. How to get your User Id and your Auth Key
To link your Picasa gallery to your app, you must get your "Auth Key" from Google, as well as your "User Id".
The procedure is rather simple.
Go to your Picasa account (make sure you're signed in):
On the upper right-hand corner of the page, click on the star wheel, then on "Settings".
In the "General" tab, you will find two pieces of information required to add the Picasa source to your back-end.
Your User Id is on the "Your gallery URL" line, in bold.
For example, (only the text in bold must be taken) :
The Auth Key is on the "Your unlisted gallery URL" line of the table, just after "?authkey="
For example, (only text in bold must be taken) :
2. Creating a Picasa section in your back-end
Once you have your User Id and your Auth Key, you can create a Photo section linked to your Picasa account in the back-end.
Fill out the information received from Google and click "Add".
Here you are! Your Picasa section is configured!
Please ensure that the photos of your Picasa album are set to Public, otherwise, the app will not be able to retrieve them.