Adding bb recipe to Yocto

Hello

I am trying to test adding Yocto recipes, I am initially trying to use the provided example example-recipe-0.1.bb, by addid the following to build_bin/conf/local.conf:
IMAGE_INSTALL_append = " example"

build fails:

ERROR: Required build target ‘mdm9x28-image-minimal’ has no buildable providers.
Missing or unbuildable dependency chain was: [‘mdm9x28-image-minimal’, ‘example’]

please advice