The nearest point you can cross on foot is the Greenwich foot tunnel a mile or two away at Island Gardens. It's probably safe enough but I'm always relieved to come out of it.
Here's a map of the DLR lines, showing where you can connect with Underground and National Rail services. If you require more specific information please post again, telling us where you'll be travelling from, or use the TfL journey planner here:
http://journeyplanner...er/XSLT_TRIP_REQUEST2