Wordpress form entry - write to database

So - I'll preface this with saying I know very little coding, a little visual basic but that is it.

I am working on a personal website project and am lost as I am not finding that Wordpress plugins are delivering what I want to accomplish.

In a nutshell, what I want to accomplish is: A user can come to this site, a form is presented to them and they can enter data into it. This data is then written to a database behind the scenes.

I have set up a new table on the database, and I have been trying to follow answers that have been given (over and over) on this site as well as others and have made no progress.

I am hoping someone will be kind enough to hold my hand enough to get me a nudge in the right direction.

When I log into phpMyAdmin dashboard the tree shows:

sitename_com -> it then branches down to the table I made called "TestTable" and then all of the wordpress tables are listed after it.

This table I set up has just three fields at the moment to make things easier in getting up to speed. The three fields are: "ID" (Key) , "User_Name" and "Location"

So my goal is to set up a form on this wordpress site that will have these three fields on it (two really - the ID will preferably auto-update with the next record value), and when submitted will write a new entry on the table.

Thanks in advance for any assistance with this.