I put one on o-ring eatch side, slide the tube in, put liquid gasket into the grove between the tube and the case. Then push in the outer o-ring, put some liquid gasket ontop of that and then add the pressplate where after i add blue threadlock to the bolts and tighten them to 15NM.
Every other way of sealing failed due to the tubing being rubbed in a bit from the outher o-ring. It has been leak free for the past 8k km. The threadlock is for precautionary matters. It's my 4th KTM and i always add threadlock or saftewire to most bolts that have the function to seal fluid openings.