I'm seeing this post so late, probably you already found a way to add this info, but just in case.. For me the easiest a way to contribute is just using iD editor in the browser, you just go to OSM, create an account, zoom on the area you want to contribute and then click edit. This editor has everything you need and is easy to use but it may be a bit daunting the first time. If you are very new to this just check how other users gave tags to the near buildings created.
For the apps, I only use them to contribute very small things like adding a missing restaurant, I'm not sure that you can even use them to draw buildings and name streets.
As a more advanced editor you have JOSM, but since you seem new and looking the easiest way, the iD is just fine.