If you have not done an Add-In before, spend a few minutes to understand how the projected is wired together. As a start look at the config.daml file and understand what the XML tags mean. One key, is everytime you rebuild the Add-In for debug you need to updated the <Date> tag to a newer date/time, otherwise ArcGIS Pro will not reload the code. Second is that in the <modules> section you define a Module ID, usually in the <insertModule id> tag, this has our className value that is used to connect the interface (partially designed in the config.daml) to your underlying code. For example, if your className="LoadMyToolCode" then you would need a LoadMyToolCode.cs file in your solution. This cs file usually only has 53 lines since its entire purpose is to load and launch your code module when the button defined in the Config.xml is clicked in ArcGIS Pro.
