Dropdown menu with HTML - Dash

I am currently building a page with the following format:

I would like to add two dropdown options in the top of the page with the following structure:
The first dropdown would get input and based on the input, the options for the second value would be populated. Based on the input received for the second dropdown, I will display the fact sheet/app given in the above link.

When I attempted to do it, I had the following problems:

  1. I cannot id the html.Div object - Gives me error

  2. Once, I get the input from second dropdown, I need to run an external function which readies the data to be used by the app given in link. - I do not know how to do it.

Can you please provide some pointers to resolve these issues.

Check out the examples from the official user guide, there is an example that does exactly this: dash.plot.ly/getting-started-part-2