Picasa's face-matching technology lets you organize your photos according to the people in them. The first time you open Picasa, it will scan your photos for new faces, since name tags are turned on by default. It can take some time to scan all your photos; however you can start adding name tags whenever you'd like. Follow these steps:
- Sign in to Picasa Web Albums.
Click Sign in to Web Albums in the upper right corner of Picasa. This lets you use your Google contacts when adding name tags.
- Add name tags in bulk or a photo at a time.
In bulk: Click on the 'Unnamed People' album in the 'People' collection. Unnamed faces across all of your photos are grouped here. Each face thumbnail in the album represents a group of similar faces, so adding a name to a face thumbnail applies the same name to all the faces in the group. To see all the faces in a given group, click the People button (next to the Photo Tray) to open the 'People' tab on the right.
Alternatively, if you want to ungroup similar faces and see each individual face, click the Expand groups button at the top of the 'Unnamed People' album.
One photo at a time: Click the People button next to the Photo Tray when viewing any folder, album, or photo. The resulting 'People' tab on the right displays all the faces that appear in the selected photos, including those without name tags.
Did Picasa miss a face in your photo? Click the Add a person manually button at the bottom of the 'People' tab when viewing the photo. Follow the instructions on the screen to add a name tag for that person. - Click 'Add a name' under any face and type a name.
As you type a name, Picasa searches your Google contacts and displays matches. Select a name from the suggested matches to add it as a name tag. Or type the name and press Enter to create a new contact -- this name tag will be added as a new contact in your list of Google contacts.
When you add a new name tag, Picasa creates a corresponding people album in the 'People' collection. Use the
button in the album to zoom in on the faces you've identified or to view the photos in their entirety.You don't have to name everyone. Deleting an unnamed face or clicking the
icon on a photo will place that photo in the 'Ignored' album. You can view the photos you've ignored at any time by clicking Show ignored faces at the top of the 'Unnamed People' album.
- Confirm Picasa face suggestions.
Picasa uses the names you add to automatically add face suggestions to your albums. If you see an orange question mark
next to a people album, go to the album and confirm these suggestions. Click 
to keep the photo or 
to remove the photo from the album. If there are multiple suggestions, you can click Confirm all at the top of the album to mark all the suggestions as correct. Toggle 
at the top to see just the suggested faces.
button in the album to zoom in on the faces you've identified or to view the photos in their entirety.
icon on a photo will place that photo in the 'Ignored' album. You can view the photos you've ignored at any time by clicking Show ignored faces at the top of the 'Unnamed People' album.
next to a people album, go to the album and confirm these suggestions. Click 
to keep the photo or 
to remove the photo from the album. If there are multiple suggestions, you can click Confirm all at the top of the album to mark all the suggestions as correct. Toggle 
at the top to see just the suggested faces.Don't worry if you make a mistake when adding name tags -- if a face winds up in the wrong people album, select the photo and click the Remove button at the top (or press the Delete key on your keyboard) to send it back to the 'Unnamed People' album. Learn more about deleting name tags.
It's easy to change the photo Picasa displays next to each album in the People collection. Within the people album, just right-click (Windows) or Control-click (Mac) the face you'd like to use and select Set as Album Thumbnail.