If you have experience with software development you should learn how to build the source. This is pretty easy on Linux or Mac systems. If not then skip this step and generate the file to translate from the source code by following the instructions below.
Generating the TS file
Using the Terminal change directory into the project folder
Generate the latest strings XML
lupdate -pro PhotoFlare.pro -ts en.ts
Copy the en.ts file to a location of your choice. Now rename to something else such as de.ts (for german)
Editing the translation
It would be recommended to use Qt Linguist to translate the strings. Follow this guide.
If you do not want to install Qt Linguist on your system replace the strings in the file like the below example in your favourite text editor:
Release for application use
Finally generate the .qm file that our application will use:
Alternatively the application will build the .qm files in <BUILD_FOLDER>/languages when you compile it.