How to use Picasa:
First, and I think this is the part you haven't done... Download Picasa.
Once you have this program on your computer, you will be able to load to the web very easily and quickly. Launch the picasa program and you'll see in the lower right corner a little gray box that looks like it is scanning your hard drive. It is. It finds every photo on your computer and adds it to the picasa organizer. It does not move or change any of your photos.
Every time I add photos to my computer, I hit the Picasa icon so it can locate the new photos and add them to the organizer. It only takes a second or two when you have just a few photos (less than 100) for it to find. The first time you do this, it will take a while because you have a ton of photos.
After Picasa has your photos all organized and in the program, you can share them online very simply.
In the lower left corner of Picasa it tells you, or shows you, if you have chosen an entire folder, or which individual photos you have selected. If you want to upload the entire folder, look and make sure it is showing the folder you want and then click the green up arrow in the bottom row, about mid-screen. That is to upload to web album. Picasa will then upload the entire folder online. Likity Split!
To select individual photos, click the photos you want to upload and then click the green arrow. You can use control click to choose photos that are not in order or shift click to choose photos that are grouped together, like three in a row or something. When I'm doing this, I choose a few and then I lock them in the tray before I click on one and lose what I hightlighted, to lock them in the tray of chosen photos, click on the green thumbtack. It's in the bottom row, in a tower of three icons, it's the top thingy - a book is the bottom one. See it?
The little book is another nifty tool. You can add to an album you already made. Select a photo or several and click on the little book, from there it lets you choose a folder that you already made and you can add your newly selected photos to it.
At this point, what I just said probably makes no sense. Download Picasa3 and follow the instructions, fiddle around with it and have fun!
If all of this was confusing, view this video for a great lesson.