Hi dkap,first download the three files ,open s-gear as standalone and press the ''presets'' button.
Go to an empty preset and press ''import''.Double click the Custom '57 file.It will be imported.
Press ''impulses''button,''import'' and double click the two other files.
Open the preset,''impulses''button,you will see my two files''Fender Bassman -1,2 and Fender Bassman AT4050- 1,2. Press 1 to put Fender Bassman to Cab1 and 2 to put Fender Bassman AT4050 to Cab2.
When you'll open your daw and your plugin s-gear you will find the preset there.
I hope you find it helpful!!!