To add new profiles in the database you can use the "User section" feature which is described in the on-line documentation :AS User-Guide 2010 EN-metric pages 119 - 121.
Referring to joints, you can "add" a joint by of the following two possibilities :
1. Create a joint from scratch. This can be done by using the "user connection" feature, described in the on-line documentation (link above) at page : 109.
In addition, you need to make sure to place the UCS when you want to insert the saved connection in the same relative position you had it when the connection was exported.
2. Use an already available connection from the Advance Steel connection vault. Configure it with your parameters and then save it in the joint library. This will make available the configured settings for other cases where you use the same joint, on similar profiles. The joint library is described in the on-line documentation, at page 98.