What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
I presume that you are looking to make all of the labels on your jotform bold.
To do that you should add this CSS code to your jotform:
You can see here how to add it to your jotform: Inject Custom CSS Codes
I would only suggest adding the CSS code to the bottom - after all the other CSS code in your jotform (if any).