"He is working as juvenile advocate. He is not running a business."

Yes he is; he is working for himself, as a Sole Proprietorship business, then.

"The client put the expenses(office supplies, printing expenses, software, laptop, conference expenses and etc) under other miscellaneous deductions in tax organizer."

You need to guide the person for what is Business Expense, what is Not (such as Asset purchase, is not Expense) and what is or is not expense when traveling (not meals, for instance).

Just because the Client fills in data, doesn't not guide you. The tax regulations guide you; you are hoping the client reveals things you need to know about, but they are not the Tax Expert. That is supposed to be you.

"The only income he received is the non-employee compensation on Form 1099 MISC."

Let's learn to Rephrase this: Your client makes money as an Independent Consultant, as an Advocate. The Advocacy program has 1099-Misc box 7 requirements to people to whom they paid $600 or more. That can be a one-time thing or someone who does this routinely.

"Should I put these expenses under other miscellaneous expenses?"

A person who did this as a one time thing has no business, so there are no business expenses.

A person who does this for a living has a business, so you need to know what is and is not a business expense. That computer might not be Expense; read on Fixed Assets tracking and depreciation provisions.

"I think these expenses are related to the income on Form 1099 MISC. But not sure how to deduct."

Have the person done this in the past year(s)? Look at their prior tax return; perhaps there is a Sched C = they are in business.

And it's time to find someone to mentor you, for you to work under.