Updating readme

README.md

@@ -12,6 +12,6 @@ For certain projects and applications it might be necessary to use a customise N
 
 1. Clone the repository via `git clone git@github.com:pmlmodelling/NEMO-container.git NEMO_container_[project_name]` where `[project_name]` is the name of the project
 2. Create a branch with the project name `git checkout -b [project_name]`
-3. Update `nemo.sif` as need
+3. Update `fabm.def` and `nemo.def` as need for the project
 4. Push the branch back to the repository and this will automatically trigger the container to by built
 5. The built container will be saved into the release in the repository under the project name