Yes, you do need to use it occationaly. You will get those revered green squares show up on your credit report, and in scoring, recent use of credit helps the score.
You might want to have a couple of cards. Use one this month, pay it off, then use the other next month and pay it off.
Just make tiny, under 20.00 charges to keep yourself out of trouble, and into a good debt to credit ratio. (that also boosts your score a lot)
Here is a copy and paste from FICO’s scorewatch, which I am a member. This is my recent score watch information:

You’ve shown recent use of credit cards.

Your FICO score evaluates your mix of credit cards, installment loans and mortgages. People who demonstrate responsible use of different types of credit are generally less risky to lenders. You helped your FICO score by showing recent use of a credit card.

You’ve been keeping the balances on your credit accounts low.

Your FICO score considers how much you owe on your credit accounts, such as revolving credit accounts and non-mortgage installment loans . Generally, the more you owe on these accounts, the greater risk you pose to lenders. You helped your FICO score by maintaining relatively low balances on your credit accounts.

I hope that helps.

Like in your situation,I would like to advise you have a look here.http://creditreport.online-helper.info/my-credit-report.html

Use each of the cards for things that you would normally pay cash for as long as you can pay the bills in full every month. I use less then $50 a month in cash and my credit card bills total about $2,000 a month. I did a credit check and all credit cards said the same thing, no late payments. My Bank on its owe FICO score has me listed at 849. I don’t owe anybody anything.

Yes it shows up, with a 0 balance. And yes using and paying off a credit card each month will improve your FICO, but a loan such as a car loan or a home mortgage is better.