Start up ReplicatorG, it should automatically connect to the Thingomatic w/ ABP and Stepstruder MK7.
Under the File menu choose Open and find the STL file that you want to print (that you designed or downloaded). You should now see a preview of the object that will be printed. You may need move the object on to the platform and/or center it.
Push the Generate GCode button, if you've moved or scaled the object it will ask if you want to save the model. You do.
Set the Object infill (%) to a value between 0 (hollow) and 100 (completely filled). We've had good results with 15 to 30 %. The layer height should be .35, 1 shell is probably good, and a feedrate between 30 and 35 seems to work well.
Click Generate Gcode and wait.
Once it has finished generating the g-code, click on the gcode tab to see it.
We've found better results (less warping) with the heated build platform set at 130° C, so you can change that here.
If the MakerBot is connected and ready, click the print button and it should start heating up to make your object.
That's the basics of it. I'm hoping to record a video of the whole process, I'll link to it here when I do.