I am not sure if you are still following this thread or not. But in order to write words easily you need a computer program such a Embrilliance. My friend that has a Brother PE770 and she uses this one.
What you want are called fonts - then you find the style you want, decide what to say, type it in and save it (as you would any computer file). You then transfer this to your machine via a USB cable - my friend is able to use the USB thumb drive. (I couldn't find if the work on your Brother PE540D, but it could. It is super easy to do. The hard part is getting it to right size. :-) If you see something do download as an Alphabet then it is the individual letters, and you have to do it one letter at a time.
You can contact Brother at their website and ask them if a thumb drive can be used instead of a cable.
Check out Embrilliance on line - it does do many things and definitely worth the money. I have a similar system for my Husqvarna/Viking, but I do have Embrilliance because I get a lot of fonts that are fun to use. (And no, I do not have any financial interest in the Embrilliance company - just love to use their program.) I will tell you where a design will start stitching, you can download more fonts to it which I cannot do with my 5D embroidery program for my Husqvarna.