T-Beam versions 1.x have a special power management chip.
For T-Beam specific things I suggest to visit the TTGO T-Beam topic instead.
Paxcounter is rather complex if you only want to write some basic code yourself.
For connecting to TTN you might want to start with the basic examples from the MCCI LMIC library as described in the topic start.
Note that you will have to use the proper pin mappings for your T-Beam version and that you have to enable/configure the power management chip (see T-Beam topic).
First try to get these basics working, from there you can extend the code with support for GPS and other things.