[HELP] Conditional Forms in WordPress

I'd like a WordPress based website, where I show a conditional form at the top of my homepage as done in this theme (A conditional search box form with an image as a background)

Code:

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Is there any plugin which can let me add such a form easily? Or, can someone share the basic code and the location where I should add the code in the theme.

Thanks for your inputs.

It's not a conditional form, this is just an search box that comes in almost any good theme. For forms and conditional forms you would use GravityForms or similar plugins.