How do you add an image to Opt in form?

Hi, i’m not familiar with html and I have looked at every post in this forum related to customizing the subscription form but nothing provides specific clear steps on exactly how to do that.

I simply want to know how to add an image to the subscription form.

In the subscription form “form code” section can I simply edit the code there and save it?

Please show me very clear steps on how to do this.