brm model not compiling

Can somebody explain to me please in a simple language what path should be in Sys.getenv('PATH') command and how to change it permanently?

I faced the issues with running Bayesian models using package brms on Mac (I downloaded package rstan and fixed C++ compiler and installed Xcode, all that seems to work fine). Here ( I read that PATH should be changed if models with brms are not compiled but I don't understand how it should look like for me. Sys.getenv('PATH') right now gives me directory inside Postgres SQL (which I worked with earlier).

Sys.getenv('PATH') [1] "/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/Applications/"