Most of the information you will require to set them up as a new employee on your system will come from their P45.
If your new employee does not have a P45 then they will need to complete a starter checklist (this replaced the P46 form)
The details provided should include:
Keep in mind that you will also have to set up a Pension scheme for your Employees. I will explain this in another post.
Click on the link for a starter checklist template new-employee-starter-form_online.pdf