Validation is what you do to ensure that it is suitable for its intended use. Validation can take any of many forms. In some cases, validation could be a review. This would probably be a very good instance where validation would better be performed by someone other than the author to remain objective (my opinion, not a requirement of the standard).
The record keeping requirment for 7.3.6 is simply that a record of the validations be kept. It could be as simple as notes that the material was reviewed by whoever you determine is appropriate to determine it is suitable for its intended use.
Very often, validation is by some sort of test. This might be from a trial run of the material in a classroom. Again, a record of the validation would be notes on the trial run and the results.