Sort out the cable length.
Decide where you are having your inline adjusters.
(Although there is one at the rear mech, so you don’t need one there, and I don’t have one on my front mech so you don’t need one there either)
Set the top of the bars in line with the stem angle (provided you’ve got a flat stem; if you haven’t got a flat stem, make it so)
Then put the flat bit of the shifters in line with the inline stem and bars.
Sit on it to check it out.
Decide it feels a bit wierd and different to your mountain bike, but embrace the difference and stop whinging.
Then run the front brake cable along the front edge of the bars, making sure that the cable is long enough to deal with the bars being turned from side to side.
Tape this cable in place with a single wrap of insulating tape at three points; where it comes out of the lever and bends with the bar, half way between the straight bit of the bar and stem, and about 1cm before your bar tape is about to end.
Repeat for the rear brake cable. You will need more slack in the rear because of how the cable runs.
Gear cables; run the rear derailleur cable along the back edge of the bar, and secure with 3 bits of tape; at the bend, in the middle, and 1cm short of the end of the bar tape.
Take time to make sure the length is ok.
I’ve run the gear cables like this on mine; I put the right hand, rear derailleur cable into the left hand stop on the frame, and vice versa with the front/left cable to get a better cable run.
Pics to follow..
Put a layer of old bar tape or foam or anything along the top of the bars from the shifters to just short of the proposed end of the bar tape for extra padding.
Then tape em up.