- Sign in to your Picasa Web Albums using your Gmail username and password.
- Select which photo you want to tag.
- Click the tags button on the right side of the page.
- Fill in the name of the tag inside the text box, enter a space separated list of tags, for example: “Wedding Flower” “Birthday Flower” Flower.
- When you’re done simply click Add and done.
You can search your photos, your friends’ public photos and certain gallery. Google indexes tags, captions, album tiltles, album locations and album descriptions. To search for a photo with a tag, simply type the tag inside the search box provided in the upper-right corner of the page. Your search result will appear in the ‘My Photos’ section.