Follow the links provided above and download the latest version 1.3.4. I have just updated my old 1.3.3. to 1.3.4 yesterday. The archive is a tar. You can download Winrar to decompress the folder. Inside, you will see a README file. Read that file very closely. If you do not have a shell account and use Cpanel, read very closely section 3: HOW DO I INSTALL GALLERY IF I HAVE ONLY FTP ACCESS?It works out of the box if you follow the directions and if your host has all the related graphic package installed NETPBM or the equivalent ones. Follow closely the chmod instructions.
Note: If you downloaded 1.3.3 there is a known warning error message related to a database line 35. Version 1.3.4 fixed that issue. So, go for 1.3.4 period.

DCASMR
my one cent. 8)