Hey mate - no such thing as an obvious or silly question, so keep em coming.

If you have auto hubs (assuming you do) you can simply go from 2wd to 4wd on the fly up to about 60klms per hour (they state up to 80 I believe but I always play on the side of caution) and the hubs lock in automatically and you are now in 4H and ready to roll - no centre locking mechanism. You need to be stationary in neutral to engage 4L and same rule applies - ready to go. Same process for going out of the gears, stopped to go from 4L to 4H but can change back from 4H to 2H on the fly.

If you have manual hubs, you'll need to put them into the locked position to be able to engage 4wd, but you can lock them in prior when you first get to dirt, sand etc and run in 2H with them locked until you need to engage 4wd with no dramas at all.

Hope this helps mate - others will have more to offer also.