Let’s first start off by opening the PSD file. Click File > Open and locate your file. It should look something like this. In the Layers panel (right side) you will click on the image in the Placeholder layer.
It will open up a new tab, and look something like this:
In the Layers Panel make sure you select the Text layer (as shown with the T in the square).
It’s likely that you don’t have the font that the PSD file was saved with. So come up to the text menu and change the font. I selected the font Harvest Wishes.
Then type out your new words in the text box. Once you’re finished, you can click Cmnd+S (Mac) or Ctrl+S (Pc) to save. This will save the new tab you had opened.
Navigate back to the original tab (in this instance, called Main Template.psd) and it should be updated! From here you can save the file or continue playing around with it until it looks the way you want. To save, you can go to File > Export As > JPG (or whatever file type you need).