There's multiple point of entries! Just do it! Define/Pick ONE core feature of your web application. Make that feature work, no one cares how you do it. Once

There's multiple point of entries! Just do it! Define/Pick ONE core feature of your web application. Make that feature work, no one cares how you do it. Once you are finished with that core feature, use it as a base for all other new features. An analogy, to create a sculpture of a head. First shape your clay into a ball, now you got your base feature. Go get them Tiger!