save file to specific location with variable save name

I have been reading up on this quite a lot and have found ones that give answers but I am still quite confused on exactly how to accomplish this. Even with the answers given I am still not sure where to even start. I am reletively new to working with acrobat and using java with it. 

I am trying to make an action button lock the text fields in the document and then save it in the alotted location and have the name "xyz.date". I found the way to lock the fields in the document and that is working well, but I am really struggling to understand how to get the file to save somewhere on its own. 

Any step by step of exactly how to do this would be much appreciated! Thank you!