How do i add name entry field to populate a certificate??

First, in you project select "Project" and "Variables".  Select "Add New".  In the name box, type "username" and the "Save" and Close.

Recommend you have a slide to "type name" here to print certificate.

Next on the slide you want to collect the text, "Insert" and select "Text Entry Box"

Change the Text Entry Box name to "username"

Then Change your "Default Text" to something like "Please type your name here"

Select "More Options" and type in the number of characters that will fit your need (i.e. 50 is enough for a name)

Next select "Variable" drop down and select "username".

More below image

Next you need to insert a Blank Slide.

Then "Insert" and "widget".  Select the certificate you want to use.

Then "Edit variables".  Turn "Name" off.

Type the Signature Name and Turn Other On and type username and OK.

That is all there is to it.

If that does not generate the name on the certificate

One the Certificate slide

Go back to the "Insert" and select "widget" and "Text Area"

Another widget box will appear and you can move the box to accommodate your selected certificate.

See image below

Are you using a certificate interaction?

Are you using SCORM? If so the variable cpQuizInfoStudentName contains the name.