"Move the transfer gear lever to the left - from either ’H’ (high) or ’L’ (low) gearbox (the warning light on the instrument panel will illuminate).:
If you mean diff lock you pull the short lever to the right then the diff lock light should light up on the dash, but beware only use it on slippery surfaces, if you use it on the road you will cause serious damage ok !
On an auto box, you need to put it into N before sliding the small lever into low ratio, I can't remember if you also need to do that for difflock? I'll check when I go out later
Your question implies that you belief you can do 'something' to more than one diff.
This is not the case. The only diff you can lock, in order to achieve greater traction is the centre diff.
What this does is to ensure a 50/50 split front to rear of the engine driving force. It does NOT change the front or rear diff, so you can and do get situations where for example you have the front and rear drivers side wheels spinning, so you go nowhere!
Only if you have lockable front and rear diffs (extra cost - not cheap) do you guarantee traction.