There is documentation at https://webwork.maa.org/wiki/LTI-Advanced_Authentication. You can also enable the debugging parameters in conf/authen_LTI.conf. Make sure that you update that file from the .dist file as it has changed considerably. You will also need to edit the conf/authen_LTI_1.3.conf file.
Note that for LTI 1.1 you use the conf/authen_LTI_1.1.conf file.
In any case you use the conf/authen_LTI.conf file and set that to load the appropriate other file (or both).