Take from the breeder's manual

Access is granted when you complete the apprentice breeder objectives.

Every week, the number of trades you can offer or accept are limited:

Less than 15 days of seniority 1 exchange
Between 15 and 30 days of seniority 2 exchanges
Over 30 days of seniority 3 exchanges
With the Pegasus Account 3 extra exchanges
In order to trade, you also must follow these rules:

Your karma has to be greater than 6
Your email address must be verified
Your account must be validated by your parents if you are under 16 years old
You cannot trade with a player who has the same email address as you
You may only make one trade with the same player per week

Hope this helps

So does that mean I have to finish all 100 of the apprentice objectives? Because I got passes and paid to unlock the last milestone thing I needed to unlock reserved sales.
Also, Thank you I didn't know about the breeder's manual.

yes access to the item exchange is the 'prize' for validating the 97th objective.