Great question, "How do I use coffee grounds in the flower garden?"  

       
    So many choices, you can spread them directly on the top of the soil.  You can mix it into your existing soil or potting mix.  Compost piles will be improved with the addition of coffee grounds. It improves the soil and encourages the growth helpful of microorganisms! 
Here is an article by  Linda Chalker-Scott Ph.D.  
that will go into all the details on how much and where to use it:  
Click on this link     Coffee grounds— will they perk up plants?