Automatically move the cursor to text input field

Am having button on my main perspective view, when I press the button, pop-up will open. In that pop-up I have a text field. Now am manually place the cursor to type something. Instead of that, when the pop-up is open, immediately, cursor need to place in the text filed automatically. I have only one text filed in the pop-up.

Share your inputs to achieve this...

You didn't spend too much time looking, did you ?

Much time already spent. Can't find the way to resolve this.

The solution is in the thread I linked... which I found in 10 seconds.