Picasa is now a discontinued application, but if you have an older version, then the Burn to CD option should be available. Firstly, move all the images into the folder that you want to burn. Insert a blank CD/DVD, enter the folder and go to Create menu, and select Gift CD. If you want to add more, simply use the button to add additional content and customize the burning settings.
Press Burn and complete the process then you can insert the CD/DVD into a compatible device to watch the images.