Okay, please let me guide you with the steps to get the certificate builder:
Certificate builder is an addon, which you find in:
Wp-admin > LMS > Add Ons > WPLMS PDF Certificates
Refer:
http://prntscr.com/ocm38i
After successfully adding the addon, go to
Wp-admin > LMS > Certificate template
(Create a new template or open existing one in edit mode)
At the bottom, you will find the certificate builder. Check this
http://somup.com/cqiQl8enmn for more help.
Hope it will help to resolve the issue. Do let us know.