From your description it sounds like you need uppercase ‘O’ as a chord root.

However, none of Finale’s chord styles will give you uppercase ‘O’ as a chord root, sorry.

But what does uppercase ‘O’ mean???

Please explain.

The better we understand, the better we can help.

Thanks for your comment, Mr. Thomsen.

Actually, I am writing a teaching material for Flute. I would like to indicate, as marking O above a note, one beat a student should count on like 2/2 or 4/2 and so on. I found using chord tool is the best. Other wise I have no idea what tool is good. I tried to use articulation tool, but it's not marked O as well, moreover, the line marked thing is not aligned. Would you give me any advice? 

Thank you. 

I would use the Expression Tool.

You can create a new expression category by duplicating an existing category (like e. g. the category Technique Text).

Then, name and edit the duplicate as you like.

For working smarter (not harder!), program expression metatools for your expressions.

That's a great idea! I know how to duplicate and create a new expression category and put what I want.

It didn't occur to me to do that. You are a genius!

Thank you so much!!!