Help a beginner? I need simple scheduling tool :)

Hi

I would like to know how to make a simple scheduling tool.

I am running a smal group training gym. I have ten instructors and we have few classes every day. How can I make a platform for this?

Every months they are sending me times what classes they can coach and then I am writing their times in a document.

I appreciate all tips and ideas.

Thanks a lot

Armen