Hi.
Which tutorial are you following to install the ESP8266 boards?
 
Regards,
Sara

Hi Sara,
I followed your tutorial at:
 
Installing ESP8266 in Arduino IDE (Windows, Mac OS X, Linux) | Random Nerd Tutorials
 
Best regards,
 
Enrique

Hi.
At which step of the tutorial you get that message? That never happened to me before.
Regards,
Sara

Hi Sara, 
Just when in the Library Manager appear Libraries ESP8266 and I click in the button “INSTALL”

You need to install it in the Boards Manager menu, not in the Libraries manager.
Please double-check the screenshots https://randomnerdtutorials.com/installing-esp8266-nodemcu-arduino-ide-2-0/

Please excuse my mistake. I really mean boards manager, not library manager. Aniway, I’ll follow your indications.
Thanks a lot.

Let me know if you succeed. 
regards,
Sara

Hi, Sara
No, it didn’t work. I get the following message:
Descargando paquetes
esp8266:xtensa-lx106-elf-gcc@3.1.0-gcc10.3-e5f9fec
Failed to install platform: ‘esp8266:esp8266:3.1.2’.
Error: 2 UNKNOWN: Get “https://github.com/earlephilhower/esp-quick-toolchain/releases/download/3.1.0-gcc10.3/x86_64-w64-mingw32.xtensa-lx106-elf-e5f9fec.220621.zip”: proxyconnect tcp: dial tcp: lookup _: no such host
Regards, 
 
Enrique

Hi.
I never faced that issue before.
I think it is because there was some sort of bug during copy paste. I think your URL on the “Additional Boards Manager URL” field is wrong.
Try copy it from here:

http://arduino.esp8266.com/stable/package_esp8266com_index.json

Regards,
Sara

Hi Sara,
My problem is over!
I was prompted by Arduino for installing IDE 3.2.3 – I did and the ESP8266 boards were loaded without problem.
Thank you very much for your advice.
Enrique Battaner

Great.
I’m glad the issue is solved.
I’ll mark this issue as resolved. If you need further help, you just need to open a new question in our forum.
Regards,
Sara