Id like to create a manual register system but am not sure how to do parts of this.. I would like to list all the names of the people in my database (tblGroup) along with a textbox next to the name. When the user clicks submit, it will add all the people with a tick in the tickbox into the DB (tblRegister)
You would do this like any checkbox but you would assign a name with  following it. For example, instead of giving each person's checkbox a separate name, you'd call all the checkboxes the same: userchkbox.
The result will be that in your action page, all the ones that have been clicked will be available to you under $_POST['userchkbox'], which will be an array over which you can loop and, one by one, insert in tblRegister.