As a noun:
* The assistant helped the manager with the presentation.
* My assistant is responsible for scheduling appointments.
* The assistant to the CEO is very busy.
As an adjective:
* This is an assistant manager position.
* He has an assistant role in the project.
* She is the assistant director of the program.
In a phrase:
* The assistant manager is in charge of training new staff.
* The teaching assistant helps students with their homework.
* The personal assistant organizes travel arrangements.
You can also use "assistant" in more creative ways, depending on the context:
* He was a faithful assistant to the old man.
* The virtual assistant provided helpful information.
* She was a reliable assistant to the team.
Remember to choose the right form of "assistant" based on the role it plays in the sentence.