Please correct me if I misunderstood, you want to submit a new record to your list on a button click, where one of the record fields has a value of YES or NO, as specified by a dropdown. If that is the case, you need to do the following:
dropdown1.Items = ["YES", "NO"]
button1.OnSelect = Collect(MyList123, { YesNoFieldName: dropdown1.Selected.Value })
This assumes that your SP list has a field named "YesNoFieldName". Please adjust as needed.
Also, if the list contains any other fields that are required, you will need to specify values for those as well, alongside the field you mentioned:
button1.OnSelect = Collect(MyList123, { YesNoFieldName: dropdown1.Selected.Value, RequiredField1: 1234, RequiredField2: "PowerApps Rocks", ....... })
I hope this helps.