Assuming that you are growing this as an annual, outside, in a container, with quality potting mix and adequate drainage...

Here are my suggestions:

The lack of blooms can be caused by too little sun and/or over watering. The plant should receive at least 6 hours of sun, avoiding the very hot afternoon sun.

Your yellow leaves sound like over-watering... Allow the soil to dry slightly between waterings. But careful not to allow the plant to wilt. Use a natural liquid fertilizer like fish emulsion to feed.

Provided you have no diseases or pests... this should do the trick! Good luck and happy gardening!