How to Autocomplete Userform from Worksheet info

Hello:
Have to admit that I'm being tested to my limits (which are very limited).
I've created a basic userform, comprising of text boxes and 1 combo box. Text boxes are ID, Partner, Territory and Deal. Combo box is Agreement.
UserForm.jpg
I've also added command buttons for Add, Clear Form, Exit and Check.
When the user enters an ID number - I'd like them to click "Check" which will then search the Worksheet for the ID number, if it exists the UserForm will be auto-completed with the information relating to that ID number. If it's a new ID number, the user completes the form. Needless to say information relating to an ID will always be the same ie: ID 8 will always be Misc/Martin/Lunch/Multi.
Can anyone help please!
I've tried running a search but that is honestly as far as my experience will take me and it's incorrect.
Copy Worksheet attached
Many thanks