Front End UI for my extension

Front End UI for my extension

I am creating an extension using ZOHO sigma and my extension requires to input start date and end date as a variables.

I want to make the front end to accept data from the user and I will store it in custom variables.

How to create a UI for this also where I can add my company logo?

Please if you can help or provide relevant help links or an example will be a great help.