QtCreator and Command Line Arguments

Go in the "Project" part on the left of QtCreator and then in the "Run Settings" tab. There is a Arguments line edit where you can put all you need to pass to your app when launching it.

For Qt Creator from Qt 5.6 Go in the "Projects part on the left and then in the "Build & Run" tab. Here you have a "Command line arguments" edit where you can put all parameters you want to pass to your app.

For Qt Creator 3.3.2, to set the working directory and command line arguments:

Projects (far left of Qt Creator)
- Build & Run (tab)
-- Run (sub tab) - brings up "Run Settings"
--- Arguments: ...
--- Working directory: ...

As the accepted answer is outdated, I post this picture which answers the question for a newer version of QtCreator:

As per the image below, Build & Run has an input for command line arguments (in the screen shot it is highlighted with a blue border as it has the focus) :-

Qt Creator with Qt version 5.6.1