Just keep an eye on this thread or your NuBits client as the rates do fluctuate with the hour. Here is a quick table as of now:

11.4 days    - ~8.5% p/a
23 days       - ~11.5% p/a
1.5 months - ~12.5% p/a
3 months    - ~13% p/a

Please make sure your select the correct period as currently no rates are offered beyond 3 months.
So if you lock in your funds for 6 months, you would only receive 13% for the first 3 months and 0% for the next 3 months resulting in only 6.5% p/a and you won't be able to unlock your funds.
The rates are like 'fixed rate bonds". They don't fluctuate during the locked period. The wallet will show the amount earned after the period when locking in the funds. What you see is what you get.

Download your wallet from https://nubits.com/download. You will be able to see the rates without owning NuBits. You will need NuBits to take advantage of these rates though.
A list of NuBits exchanges is here: https://nubits.com/exchanges. CCEDK has USD/NBT and EUR/NBT pairs for your fiat as the others have BTC/NBT pairs for fast trading.