1- Register on the digirails board so you can access the downloads
2- Log in
3- On the index page, scroll down until you see a section named "DigiRails DownLoads"
4- Choose a forum, for example "RW Locomotives"
5- Choose a thread, for example "Default GP-7 +GP-15"
6- Find a download link in the first post, for example "file Download Link
http://www.mediafire.com/?c5cafb0hj0cbx03"
7- Click on the link, get a big green download button that says, for example, "gp7_sal_a2rwz.zip" and "Download (4.46 MB)
8- Save the zip file somewhere on your disk
9- Open the zip file and extract the contents somwhere on your disk
10- In the contents, find instructions, for example "README_GP7.txt"