How do you use past participle without using be verbs?

Answer 1

In a participle clause.

A participle clause is a subordinate clause where past participle is the main word.

eg

The police are looking for a young man known as 'tagger.'

Accused of fraud the official resigned.

Once taken the drug has a mild effect

Answer 2

You can use past participles in a sentence as an adjective to describe a noun. For example: "The book read last night was interesting" or "The cake baked for the party smelled delicious."