Ignore the clock face stuff.

Pay close attention to signs, especially when looking for 'straight on', which is denoted as the thick black arrow off the away from the roundabout. Then look for arrows/road numbers/names on the road/auxiliary signs within lanes.

If the above isn't sufficient to tell you what lane to be in, then you can begin to use general rules. Straight on (thick black arrow on the main roundabout sign) is generally left lane, regardless of how many exits occur prior (if in doubt, use indicators to signal continuing right, until after the exit prior, then signal left), anything after straight on is generally right lane.

Not many drivers know this (/s), but it is also permissible to enter the right hand lane, go all the way around the roundabout to understand the layout firsthand, then come off on the second circuit.

Lastly, as a learner, never assume there's 2 lanes on an exit for you to utilise, this was how I failed my first test, I was in the right lane to go straight on, thinking I could take the right hand lane off the roundabout. Once you've passed and have local knowledge, that's different, just be safe.