compiling sonoff.io

I'm trying to use Sonoff with the Arduino IDE.
I followed the instructions (downloading the zip file from Github and place the files in the appropriate directories).
The instruction says try to compile Sonoff.io.
Doing that I get the following error message:

Arduino:1.8.9 (Mac OS X), Board:"Generic ESP8266 Module, 80 MHz, Flash, Disabled, ck, 26 MHz, 40MHz, DOUT (compatible), 512K (no SPIFFS), 2, v2 Lower Memory, Disabled, None, Only Sketch, 115200"

/Users/yvonnedevries/Library/Arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-3-20ed2b9/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld: sonoff.ino.elf section .irom0.text' will not fit in region irom0_0_seg'
/Users/yvonnedevries/Library/Arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-3-20ed2b9/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld: sonoff.ino.elf section .text' will not fit in region iram1_0_seg'
collect2: error: ld returned 1 exit status
exit status 1
Fout bij het compileren voor board Generic ESP8266 Module

Dit rapport zou meer informatie bevatten met
"Uitgebreide uitvoer weergeven tijden compilatie"
optie aan in Bestand -> Voorkeuren.

Could you please give me some advice what to do.
Thank you in advance.

Yvonne