Once you have downloaded and started Picasa it will go out and find all your photos. The Picasa Main Screen is an easy and intuitive way to manage your photos.

Picasa 3.0 Main Screen
When you begin using Picasa you should take a minute to familiarize yourself with the Main Screen. The largest area is made up of thumbnails of your photos. You can scroll up and down through all of the photos and it scrolls automatically from one folder to the next. In the lower right corner is a slide bar which allows you to size the thumbnails up and down. You might want to size this down to search for a folder of photos of a topic – perhaps last summer at the beach or a series of flower photos. You then might slide the slider to the right and enlarge the photos when trying to locate a specific photo.
Once you click on a photo it is selected. You can see what is selected in the lower left corner of the screen. You can select multiple photos by holding down the CTRL key and clicking on each photo you want to select. You might want to select a group of photos to copy or print them – but more on that later.
On the left hand size of the screen is the list of folders that have been found by Picasa with photos in them. These can be displayed in a list or in a tree structure. There are two buttons above this area which toggle between those two display formats. The drop down list allows you to select how you want the folders ordered. I like to see my folders in a Tree Structure, sorted by Name.
Finally in the upper right part of the screen are ways to located and filter the photos. You can find photos containing a specific word in the folder, description, caption or filename. You can also filter them to find only the starred photos. These capabilities become more powerful as you identify your photos when you upload them.