What is a Gerund?
Examples : The man enjoyed reading.
The gerund would be reading
The boy hated running.
The gerund would be running
Examples : The boy loved playing soccer
The gerund phrase would be playing soccer
The old man loved walking outside
The gerund phrase would be walking outside
How to use Gerund Phrases
The man was running
This is not a gerund phrase. it does end with an ing word but the word running is used as a verb not a noun. You can tell because the word was is used making this a participle phrase instead of a gerund phrase.
The man liked running
This is a gerund phrase because the word running is used as a noun. The word liked causes running to function as a noun. Verbs ending with an ed modify verbs with an ing to be used as a noun.