This is very easy to install syringe pump. You conect the the syringe with a fishing line (or a strong string, 1mm diameter) via a bowden tube to your extruder motor (see the hex screw). You connect your string with the spool attachment to the extruder motor shaft. Now the string winds around the shaft and pulls the plunger down and the syringe extrudes whatever you filled it with.
I used a 100ml syringe, and printed a small attachment, to get a 1.9mm nozzle. A smaller syringe works probably better (because physics ;) ). For this setup i used the same parameters as if i was using a pen holder (see my other thing) and turned the flow down to 10%. The flow rate can vary with your nozzle diameter, your syringe and the liquid/paste you are extruding. I used icing made from 125g of powdered sugar and 2 tablespoons water.
Expect some fiddling around to get good results!