Hi @Anonymous,
You need to create connections to both the two SharePoint under Connections with correct credentials.
About how to manage connections in Flow, please check this doc:
https://docs.microsoft.com/en-us/flow/add-manage-connections
When configuring the trigger or action, click the “…” then select the connection you want to use for the trigger/action under My connections.
Please take the following screenshot for a reference.

When using the trigger “When a file is created(properties only)”, it won’t return a dynamic content for file content. So please add another action “Get file content”, then you could use the dynamic content “File content” for the Create file action.
Best regards,
Mabel Mao