If you mean "How do you remove the watermark?" the best method is to just go back to the original file (hopefully you saved it) before the watermark was added.
Is it your photo or did you get it from somebody?
If the watermark is 'embedded' in the pixels of the photo, then it is fixed. Only extensive editing might be able to remove it.
If you have the original 'master' photo file in Lightroom you could export the derivative photo again with a corrected watermark.
Its my photo.