You will need to get a piece of metal tubing to put into the stove pipe, a foot or two will do. Attach the rubber tubing that came with the Dwyer to the metal tubing (inside or out, whatever works) Put oil in the meter, mount it level and zero it. Attach the rubber tube to the low side of the meter, so that when checking draft, the oil will be pulled to the right (more range that way). The high side is left unhooked. You will have very low draft when the chimney is cold, but it will build as the fire brings the firebox up to operating temp. Check the draft after the fire is good and hot and the intake damper has been open for a while. The baro should be set so that the draft never goes over -.06" WC (or the sixth mark right of zero) Once the damper has been closed for a while and the fire has settled into "cruise" mode, the draft should remain above -.04" WC until more toward the end of the fire, at that point the draft will drift back toward zero as the fire burns out and the chimney cools.
As for checking static pressure, I have never done it, but maybe one of the others can elaborate on that, or look it up online, I see there are lots of pages come up. Looks like plenty of info on You-tube too...