Hi Trotters,
As mentioned above, steeping is when you leave bottles for a few days (maybe longer) to allow all the flavours to fully mix.
Different flavours will have different steeping times so it will be a trial and error process.
Majority of ready made juice you buy from vendors will also need steeping for a few days, best way is to ask the manufacturer how they recommend you steep it.
I usually leave to steep for 5 days with the lid on, shaking twice a day, and then take the lid off for another day.
I also keep mine in a dry dark cupboard which works best for me.
You can heat the liquid up to speed up the steeping process as mentioned above, but heat will reduce / ruin your nicotine levels, so I wouldnt advise it.
Thanks!