PS Texts are standard text objects that can be used over and over. They can be created in the PS Text catalog or directly in the project. Once you have either created or assigned a PS Text to a PS object you will see them in the CJ20N structure.
To assign a PS Text to a network activity, select the NWA on the structure and then on the right hand side there is a PS Text icon in the list of Overview icons.
To create a new one, right click on the PS object and you will see create, PS Text.