you have already done the most difficult part, downloading the software.

The downloaded file is in your Downloads folder. Open that folder, by default it is at the right hand end of the dock, and find the file you downloaded.

It should be called "picasamac.dmg" (without the quotes). If it is not called that, then you downloaded the wrong file. If your files has .exe on the end, instead of .dmg, then you have the Windows version of Picasa. Go back to the Picasa site and download the Mac version.

Assuming it is correct, double click it. This will bring up a little window that says "opening picasamac.dmg"
It happens quite fast and then goes away.
On your desktop you will now find a disk looking icon with the name Picasa 3.9.9 Double click that.
In the window that opens, you will see the multi-colored Picasa icon. DO NOT double click it.
You are going to drag that icon from there to the applications folder. First open the Hard Drive and find the Applications folder. Arrange the HD window so that you can see the Picasa window and the HD window at the same time.
When you open the HD you will see the Applications folder in two places. In the left hand pane of the window and in the main right hand pane. Either one is good.
Now drag the Picasa icon from its window to the applications folder. When the + sign appears on the Picasa icon AND the icon is over the Applications folder, let go of the mouse.
that's it. All that is left to do is close the Picasa window and drag that disk looking icon into the trash.

It may sound long winded and complicated when it is broken down into steps, but it really isn't.

There are not many applications written for the Mac that have actual installers as there is not the need to place bits and pieces of an app in obscure places, like there is in Windows. Some apps have a shortcut to the Applications folder built into the downloaded file but, as you can see, Picasa does not.

Let us know how you get on and also what Mac you actually have. iMac or Macbook

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