want to add button on ribbon?

Hi ,

I want to add a button on ribbon on diplayform.aspx page. Actually .. when I click on list item it will opens a window ie DisplayForm.aspx page. Here I wanna display button(Delete) on top ribbon for logical deletion of the item. When click on this button(Delete) item will go to hide state. For hiding item already i wrote .js file . 

Anyone please help me to add button on ribbon and how to add my js file to onclick of this button.

Appreciate if anyone solve this.

Thank you.