Put this in your init.el file:
;; Chargebee
(load "~/<clone-directory>/chargebee.el/chargebee.el") ;; replace <clone-directory> by the directory where you cloned the project in
(use-package chargebee
:ensure nil
:custom
(chargebee-api-server "your-api-server")
(chargebee-api-key "your-api-key"))
C-c g
: Reload chargebee customer buffer