Take a photo of the handwriting, copy/paste it to lightburn. Select the image, then trace image. Depending on what it was written on you may have some or a lot of work ahead of you removing lines or cleaning up the writing so it's legible. 

I use edit nodes, breaking shapes and extending lines where needed. Always make sure you have closed a shape you broke before moving on.

If your customer wants the writing thicker, what I have done is use the offset shapes function in LB. You'll have to play around with it as far as size, I typically go around 0.0125 with outer shapes only. Then I'll pull that offset away and if the thickness is good, I'll approximate any missing loops or gaps in the lettering as needed.