That's not consent, then. It's impossible to actually consent to something without knowing it.
As soon as you upload a file or add an Action, a checkbox, which is HIDEN by default, will appear, enabled. This serves as your agreement to have your conversations contribute to model training. Keep in mind, this option will only show up after you've made an upload or added an action.
It was almost out of my sight, did you notice it right away?