To load an existing protocol from a repository to a task, go to the experiment overview and open a task. When in Protocol steps overview, you can see the green Load protocol button. Click on it and select from repository to upload a protocol. Choose a protocol from a list of protocols stored in the repository and finish the action by clicking the Load button. Since the purpose of loading a protocol to a task is to link the task with exactly one protocol, you cannot upload multiple protocols to one task.
To learn how to load a protocol from a repository to a task, see the GIF below.
Please note that this action will overwrite the current protocol in the Protocol steps overview and unlink it from repository. The current protocol will remain unchanged in repository. In case you have an empty Protocol steps overview and you load a protocol from a repository nothing gets overwritten.