In the secrets TAB you simply insert you SSID and password.
IIRC they can also be used in an alternate fashion such as setting up an AP to use them as logon credentials.
The secrets tab allows you to share your sketch with others but without divulging your wireless credentials.
Not all examples should have that as some simply dont use them.
If you need to modify the sketch to take out the secrets you should delete the secrets tab and then modify the call in your main sketch.
Change "SECRET_SSID" to "SSID"
Change "SECRET_PASS" to "PASS"
Doing it that way will also slightly reduce memory size too.