To do this, you can follow the tutorial "Uploading files to file system" here.
Once the tool is installed , you must compile your sketch with " Flash size = 4M (1M spiffs )" options .
When you tried to compile with this option, you will have a link problem saying "cannot open linker script file eagle.flash.4m1m.ld: No such file or directory".
To resolve this issue :
- Go to the directory " esp8266 \ hardware \ esp8266 \ Version \ tools \ sdk \ ld "
- Copy the file "eagle.flash.4m.ld " and rename it to "eagle.flash.4m1m.ld"
- Change the line PROVIDE ( _SPIFFS_start = 0x40300000 ) ; by PROVIDE ( _SPIFFS_start = 0x40500000 ) ;
Now it should compile.