First, I recommend not displaying the login form in the Content Blocks. They can be disabled on the Connections : Settings admin page under the Display tag. Disable the Login Form option in both the Result List Content Block and the Single Entry Content Block section.
It is best instead to add the login widget to the theme’s sidebar.
This will give you a more presentable directory.
Now, while on the same settings admin page scroll to the Result List Actions section and disable the “Submit New Entry” option. You only want this enabled when you want to show the link to allow anyone to visit and submit entries to the directory. Since you only wish to have registered users submitting their entry, you do not want this to be enabled. Many users wish to have both which is why it can be turned off/on.
Make sure to follow the Link configuration instructions.
You can require login to view the form too, here is the link to the docs with the steps to enable it.
Hope that helps!