Click on "CHANGE CHALK SHAPE OR TEXT HERE" layer. Right-click and select Edit Contents. New document with *.psb extension will be opened. Place your custom shape or text under layer folder. Save and close, document will automatically be updated.

PSD | 300 DPI | 5457 x 3683 px | 350 MB

https://creativemarket.com/grasycho/670929-Chalkboard-Solution-PSD-Template