Hmm... not sure why you'd want to work with Picasa if you're already on Google Plus since they do seem to use the same underlying database (that is, photos uploaded to Picasa can easily be shared on Google+ and photos uploaded to Google+ show up in your Picasa account once you've connected the two), but I'll run with it because, well, that's what we do here at Ask Dave Taylor!

I will say one difference between Google Plus photo management and Picasa is that the latter lets you specify which picture you'd like as your 'album cover' image, which is nice. Unfortunately, it doesn't seem to actually work on G+, as you'll see if you pay very close attention to the sequence of photos in this tutorial.

Let's jump in! To start, hop over to picasaweb.google.com. On the top right you'll see an "Upload" button:

Next step is to specify an album name before you start uploading the images themselves:

Okay, to be fair, you don't have to specify an album name, but why not help people know what they're going to see? For my demo, as you can see, I've specified Colorado Pumpkin Patch.

Meanwhile, same screen but a bit lower, there's a convenient drop target that lets you just drag and drop your photos onto the Web browser:

Being ever curious, I decided I'd drop a folder full of photos onto the target zone:

Unfortunately it didn't work.

Instead, I needed to drag the individual photo files:

Instantly Picasa starts uploading the images and shows you its progress both with the little bar along the bottom and with the thumbnails that gradually appear:

Much time passes (or very little time passes, depending on your album size and connection speed) and it shows thumbnails of all your uploaded images. But you're not done yet:

Notice on the right you can enter an album description where it ingeniously says "Click here to enter an album description". Notice the yellow text box too: "You haven't shared this with anyone".

We're not ready yet. Let's enter a description first by clicking on... well... you know...

Anyway, here's what you see:

I've entered a rather long description and a city, state pair to specify exactly where the photographs were taken.

Most important on this page make sure you set the Visibility to public if you want the photos to be publicly accessible. Look at the bottom of that picture above.

Have everything set as you'd like? Click on "Save changes".

Before we share this album, however, I'm going to make sure the image I want is the one featured in the Google Plus photo album display by viewing that individual image...

.. and clicking on "Actions":

I'll choose "Set as album cover" and now, finally, I'm ready to click the "Share" button:

The result is a nice display of the images and all the input fields we expect from Google Plus (which is where it's going to share it with your friends and family):

Didja notice what didn't happen, though? The pumpkin image set as the "album cover" is the one I hoped would be displayed as the largest image, but it doesn't. Perhaps some day it will work, but if nothing else, this shows you how you can use Picasa to upload a photo album!