Cannot find and install fsl-first-data

I tried to use 5ttgen while reported:

5ttgen: [ERROR] Atlases required for FSL’s FIRST program not installed; Please install fsl-first-data using your relevant package manager

I tried to fix it by install fsl-complete while reported:

Package fsl-complete is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'fsl-complete' has no installation candidate

What should I do to fix this issue? Alternatively, is there any way else to generate 5tt format image? Thanks