To access symbols in SwiftKey, press the ‘123’ key in the bottom left hand corner of the keyboard.
On iPad this key will look like:
You can also access the standard iOS accents by tapping and holding letters that have other characters associated with them and sliding your finger to the desired character.
Read here to learn more about punctuation on SwiftKey.
For further help in accessing symbols, please see this instructional video:
Video captions are available here.