Currently there is not a direct connection from Picasa to Revel. So you would need to download your images from Picsa to your computer or mobile device. Then you can upload the photos to Adobe Revel thru a web broswer by logging in with your Adobe ID at Adoberevel.com, or using your computer or mobile device
Please see our FAQ Forum post "How do I share my photos in Revel" http://forums.adobe.com/thread/1157995?tstart=0
and "How to upload and download images to Revel" http://forums.adobe.com/message/5106054
While Revel offers some of the top features from Photoshop.com, it doesn't offer everything. We know that can be frustrating. We are working very hard to deliver more capabilities and expand onto new platforms, devices, and file formats. But we need your help. Please give us your thoughts Adoberevel.com/support on how to make Revel a better product.