If you are talking about e-signature, not docusign, below is the process.
We have sgnEmployee field in the form which is specially designed to capture data regarding who and when sign the form. New hire can sign the form by clicking on sign form button in signature step.
When you click sign form sgnEmployee field will capture your name and current timestamp which will display in the form with a tick mark in blue color.
In custom form you can design this feature by defining the field property as sign and select employee from drop down if you want to capture employees signature.