Beats with ILM

I am using Elastic cloud and have configured an Index Lifecycle Policy.
We initially had a trial period with Elastic and have started pulling in data via filebeats, winlogbeats etc, which have created their own index templates, indices.
How do I now add the new ILM policy to these existing beats?
I want the same policy to cover all filebeat/winlogbeats ingestions that we have from the trial period.
I have been looking over the documentation but I am still needing some assistance.
From what i can see there are 2 areas to cover:

  1. All new indices to be covered by the ILM.
  2. Update existing data to be covered by ILM.

Any help would be appreciated.