F1 help in Webdynpro Application

Dear Gurus,

I have created a webdynpro application. In the application i have 2 input fields.

1) Purchase Orderl Number  (Standard Field).

2) Time frame  (Custom Field).

Now on the PO Number Input field, If i Press F1, The standard f1 help will display saying Purchase Order Number.

Now on the Time frame input field, If I press F1, "Time Frame inforamation" should be displayed.

What are the different ways, I can achieve my requirement ?.

[Note : Please dont suggest me to check online. I have done that and i couldnt understand those, thats why i am posting here]

Thnaks in advance