Copy this Tinkercad file into your Tinkercad profile and open it as a project:
https://www.tinkercad.com/things/erTogrfReeW?sharecode=AzVm-F1gLKuTE5cU15f60PQkT1MJvHIBXc58HgXc8ms

First, select the pendant, then select the Ungroup button () to separate the Pendant from the letters.

Select just the letters. In the Properties for the letters, enter your initials into into the Text box

After you enter your initials, select the pendant, hole, and the letters and press the Group button () to group them together.

Export the pendant from Tinkercad as an STL file. Select the sign, then press the Export button. Ensure that The selected shape is selected under Include, and press the STL button. The pendant uses Prusaslicer's color change option. 

Use the layer slider in Prusaslicer to select the first layer where the letters appear (if using 0.2 mm layer height, this should be 3.2 mm), then click the “+” sign on the slider to set a color change at this layer and re-slice. Use the layer slider to double check the color change point.

Leave a comment if you have questions and I'll be happy to assist! Post your make and please give it a Like if you are happy with your pendant!

Happy Printing