Rick explains in this short video how to change the window frames to fit the log thickness of the cabin walls.
The doors and windows supplied will have a special U channel type frame. This channel receives the thickness of the wall logs around the door or window. The channel creates a floating frame in the wall which is important to allow wall logs to swell and contract in height around the window or door naturally and unimpeded and without distorting the door or window.
There is to be no direct fixing of the door or window directly to the walls. It will be noticeable that there will be a particularly large clearance between the underside of the wall log that spans over the door or window and the top of the window frame at the root of the U channel. This clearance is critical to allow the walls either side of the door or window to contract in height which causes the log spanning the window or door to drop down deeper into the U channel.
Expect to see a clearance of about 20 mm but more or less is common at assembly time, it all depends on the dryness of the wood at the time. Please do not be alarmed by this, it is a technically clever way of dealing with the natural behaviour of wood which if not dealt with correctly by allowing the natural freedom of movement, would cause no end of problems as it swells and contracts in different atmospheric conditions.
The U channel is formed by a machined step around the window or door plus an architrave to act as the other leg of the U channel. The window or door will have been shipped with this architrave pinned in position (not fixed, just pinned for transport and easy to pull off by hand). The gap between the legs of the U channel needs to correspond with the log thickness of the cabin. Normally the doors and windows are shipped with a 28 mm gap and if this is correct for you, run some screws through the architrave into the frame to make the U channel rigid.
The architrave has a 5 mm step on one face so by turning it over it increases the gap by 5mm from 28 mm to 33mm. If you need the gap to be 33 mm wide, then mark the existing position of the architrave on the frame, pull off the architrave removing the pins, and turn the architrave over and refit it to the marked positions this time by screwing through it into the frame.
If you need the gap to be 45 mm or 56 mm the procedure is as for 33 mm but before re-fixing to the frame there will be packer pieces provided to fit between the frame and the architrave. The packers will either be 12 mm thick to increase the gap from 33mm to 45 mm or 23 mm thick to increase the gap from 33 mm to 56 mm. It can be easier to pin the packers to the frame, aligned with your marked position, and then place the architrave on top and run the screws through the architrave and packers into the frame.
You have the choice, either prepare the doors and windows as described and build them into the walls as you stack the wall logs OR build the walls which automatically creates the apertures for the doors and windows and later on insert the doors and windows from the outside and fix the architrave and packers from the inside to stop the frames falling out.