The installer says "Ce logiciel ne peut pas être installé sur cet ordinateur." (This software cannot be installed on this computer.) Solution: You are likely on a Mac newer than 2017, or the system date is incorrect. Sierra rejects installations if the system clock is set after 2019 (due to expired certificates). Open Terminal from the Utilities menu and type: date 0101010117 to set the date to 2017.
Due to the file size (approx 4.8GB), you will need a Dual-Layer DVD (DVD+R DL) to burn this ISO using Disk Utility or a third-party burning tool.
In the Storage settings, select the macossierra10126french.iso file as the Optical Drive.