Threaded rod should pass through the holes in the printed frame pieces relatively easily; ream the holes well. The threaded rod can be used like a file to open up the holes a bit more.
Some of the M8 nuts must be threaded deeply onto threaded rod, which can take time. There are a few ways to speed it up, one of which is to start the nut and then roll the nut across your hand by moving the threaded rod with the other hand. If a package of M8 nuts, washers and/or bearings must be advanced along the rod, it can be done semi-simultaneously using a similar method.
With an 8mm drill bit and a piece of threaded rod, thoroughly ream out all of the 8mm holes in the apexes, using the threaded rod as a file. These parts are quite durable and they are unlikely to break; be aggressive. The threaded rod should pass through the holes relatively easily.
Parts for one triangle.
Put a rod clamp on one 370 mm rod with a washer and a nut on both sides. Don't screw it tight; you'll need to adjust the position later. Put a nut and a washer on each side of each rod.
Put the triangle together. Make sure the clamp goes between the footed vertices and the feet are both on one edge of the triangle.
Repeat for the other triangle.
With the 290mm wooden jig, space the vertices such that the flats near the nuts tightly hold the jig between adjacent vertices and tighten the nuts. Repeat with all sides of the triangle on both triangles.
Top base rods.
Assemble the two top horizontal rods for the base (290 mm), which will go through the top holes of the footed vertices. The image shows the pieces for one rod, and another rod assembled.
Assemble the horizontal rods for the top of the frame(440 mm).
Bottom base rods.
Assemble the bottom horizontal rods for the base (290 mm).
Attach the horizontal rods to between the triangles. The bottom frame rod with the nuts and washers on it is the front of the machine. The extruder will be on the left of the top rods, so leave more space there than on the right. The top horizontal rods on the base have one nut on one side, and two nuts on the other. The side with one nut goes to the right.
With the 234mm wooden jig, space the horizontal bars equally between vertices tightening only the nuts on horizontal rods at the base. The top horizontal rods will be spaced and tightened later.