What/How to write in an introduction of a descriptive essay?

[DarbySchnoebelen]

I already picked my topic. I'm describing getting flowers from a love. I have to prove a point throughout the story. (My teacher wants the Thesis statement to be in the introduction.) The thesis has to have an arguable point. Mine is "It is not a wast of money to buy flowers, even though they will wilt and die." I'm not sure what to put in the introduction nor how to write it.