Hi misstwiggley,
Start a thread with a list of what you are looking for and what you have to trade and other members with an interest will respond. You can converse via tree-mail with personal information like address, etc.
Just be aware of this message from the site administrator:
The Plant and Seed Trading forum is available for members to organize amongst themselves, the trading of plants, seeds and garden related items. This forum is not moderated and there are no rules so it's "Trader beware, be careful, treat each other respectfully and have fun."