I am trying to install the firmware for this printer. 1.1.9. MKS GEN_L v1.0 board. dual extruder etc. Find the downloads on github, and it seems simple enough. Download, unzip, click MARLIN, click Marlin.INO, verify in Arduino IDE, upload. Problem is when Arduino IDE opens, there is only the one marlin tab. No config.h tab, like all the videos show. If I try verify, I get error message config.h file does not exist. What am I doing wrong?