Filling in missing parts of a Photogrammetry Mesh

I am new to 3D Modeling and how it relates to Photogrammetry.

After exporting my Obj into Meshlab to clean it up and removing unwanted materials, I import my OBJ into blender to start doing the real work. My biggest issue is that I am not an artist so I am looking for an idiot proof way to fill in gaps of my model, or add on to missing parts. In the attached link you can see I have a statue that is missing parts of the hat, or even the bat. What tool would be best to correct these areas?
https://drive.google.com/a/acm123.com/file/d/12NXIx6OT8-5RYtv7woVN2t1RmOhLqCsU/view?usp=drivesdk

I tried posting something before but can’t seem to see my original post, so sorry if this is a duplicate

Screenshots please.

There is fill holes operator, did you try that? Mesh;ab also has some gap filling tools.