How can I add, modify and edit fields to the signup form for new subscribers?

How can I add, modify and edit fields to the signup form for new subscribers?

I think this should give you the basics, Customising Subscribe Page

Howdy,
The page Subscribe page design ... | phpList manual did not really help.

1 — New Input Field.
My question is the same as Buylocalgateway asked: How do I add input fields to the Subscribe page?
I want to add a NEW INPUT FIELD to the form - such as …

Company name: {input type=“text” name=“CompanyName” value=“”} {bR}
Company Website: {input type=“text” name=“CompanyWebsite” value=“”} {bR}

I guess my main question is: what do you call a form field, or input field, in pHpList?
All I can find are “attributes” and other non-standard HTML names.

2 — HTML Coding.
I also would like to know what types of HTML code are allowable in the page customization? Example: edit a subscribe page / General Information / Thank you page seems to only allow the HEADER tag {H} … but I need to create a text link. Using the simple markup “{a =” …_blank"} TEXT {/a}" code does nothing.

I hope this question can be answered.
~ mark