Conditional field (step by step)

Conditional field (step by step)

Hi -- 
(I already posted this, but as a reply to an "Answered" topic. I'm reposting it here for clarity's sake ; sorry if I'm breaking forum rules)

I have a radio field : "Gender" with Male/Female as possible values.

I would like to display a text field "Maiden name" only if Gender = Female
If I try this :

if (input.Gender == Female)

it says "Female" is not declared as variable.

I tried to use "Set variable", to no luck so far.

Would a kind soul provide a step by step tutorial for this?

Many TIA's.