Accessible at http://plotter.local

• Consider levelling the bed. Currently this is a manual process.
• Put a scrap piece of paper on the bed of the plotter.
• Set the printer's Z co-ordinate to 0.
• Unscrew the M3 bolts on the toolhead.
• Put a pen in the toolhead and allow it to touch the paper.
• Tighten the M3 bolts, you'll want to use a decent amount of torque to ensure the pen doesn't wobble left-to-right as the plotter prints.

You can use this inkscape extension to generate gcode from an svg. There's a good tutorial on how to use this extension towards the bottom of this PDF.

Make sure that you have correctly set your working Z-height for your pen, and have set the right x/y starting/ending points. It's a good idea to double check this by moving the toolhead in mainsail to reasonable starting/end points (lower left, upper right).