How to use your own customized button and text box?

I have made a multi page form for my mobile phone trade in website.

I simple sequence that asks users inofmration about their phone.
I want the form to compliment my current theme 

Can i use custom textbox and button by editting the HTML?

If so, how ?
If not, how can this be done ?

Hi, please share with us the form in which you would like to customize the buttons and textboxes. Also, provide us details of what you want to accomplish, we will be glad to assist you.

I was forgetting to mention that this can be accomplish by adding CSS codes in your form, to customize the submit button etc.