Hello Luc,
first of all, please try to build the example 'Hello World' as described with the GCC toolchain. This ensures that the installation is correctly done.
Unfortunately you did not mention, which Target (which Build Environment) you are using and which version of the IAR compiler you are using.
If you are using a supported version of IAR, then you can follow exactly the description concerning the IAR usage within the Getting Started document. There is no need to "fix" something.
If you still have the problem, please try to provide some more details.
Best regards,
Manfred.