SlingStudio does not support PAL video sources. SlingStudio works only with video sources that support NTSC resolutions.
That said, many PAL cameras support the NTSC format as well.
Such dual-format cameras should work with SlingStudio as long as they:
For more information on what these items mean, see the article linked below: Does my camera work with SlingStudio?
Not sure if your PAL camera also outputs NTSC at 30 fps or 60 fps? Check your camera's user guide for more information.