Hi Rox - I'll take a stab at this. It can be a bit confusing, and I'm sure that others will correct me if I make an error here.
Let's say that you are a Gold Elite member of Marriott Rewards. The base number of nights needed to earn Gold is 50 in a calendar year. Those 50 can be earned in any way - actual stays, via the Chase Marriott Rewards card, or through Marriott promotions. Let's say that by the end of the year, you earned 60 nights, 10 more than needed to renew your Gold status for the next year, but 15 fewer than you need to attain Platinum status. At the end of year, Marriott Rewards "rolls over" those 10 nights, so you will start in January with 10 nights, not zero nights. I'm not sure what you mean by "how do I access them." The number of rollover nights from the previous year will show up in your Marriott Rewards status box which shows your current accumulated points available for points redemption (for your total cumulative points earned, after redemptions, you need to call Marriott Rewards directly).
I hope this helps and if I left out anything really important in my effort to simplify the concept, I'm sure that others will add their comments.
tef and nhtraveler,
Thanks for your responses. I too am just learning how all of that works. Here's another question then. Let's say I am Gold and I only earn 45 nights this year (I didn't start out with any rollover nights, so they're all "legitimately" earned). So not meeting the 50 minimum, I would expect to flop back down to Silver. When I flop down to Silver (which only requires 10 min. nights, I think), will I start with 35 rollover nights?
Thank you all for your comments. I must not have used the proper search content (unusual but I will figure this site out). In any case, I understand the roll over of excess stays (not needed to acheive the next tier).
As far as the 'access' question, I was confusing it as an earned award being rolled over.