You need to install Magisk and install camera2API for gcam to work. To do so, use the search bar for this device. There are pretty neat tutorials on how to install magisk and gcam. Let me know if you cannot find them, but please, try.
So, first, install Magisk and root your phone (alltogether). Then, download and install camera2API with the magisk manager app. Then, install a gcam app. And that's it. Post any doubts in the corresponent thread.
Since you are new, you must know a couple things (someone correct me if I'm wrong).
Magisk is a tool to root you phone (and much more). It also has "modules" to "tweak" your phone from within (eg.: camera2API enabler)
To root you phone is to gain access to the belly of the beast. To be able to modify things otherwise locked. For you and for the allowed apps, so be careful with what you grant root access to, afterwards.
To flash something means to install somethin into the flash memory (just follow the instructions for this one).
Fastboot is a "state" o "mode" that your phone gets into, where Android haven't started yet, and it's ready and waiting for instructions on how to proceed (or install) from a PC (usb). You can get into it holding vol- and power with your phone switched off.
