Sondi, welcome!!
In order to add seeds, I find the easiest way is to go into the seed swap that you're participating in and click on the link that says "Manage your own swap list". From there, you just type in the name of the type of seed that you have, one at a time, and create the entries. This is particularly useful for seed types that might not be in the system or for hybrid seeds (or seeds for which you aren't sure of the exact cultivar).
I hope that helps!
