Here you will find the full information on charging your smart.
As with any other connector.
Just unplug and away you go.
If you charge for 40 minutes with the optional 22 kW charger, this will take you from a charge state of 10% to 80%.
If you charge your smart with the 4.6 kW on-board charger at a wallbox or charging station.
When you hook up your smart with 4.6 kW on-board charger to a common household socket. 
Simply charge your smart at a common power socket or at a wallbox.
When you're out and about, you can charge your smart at a wealth of public charging stations.
Fast charging at a wallbox and a charging stations with the standard cable.
With this optional cable you can charge your smart at any domestic power socket. 
 The specified values were determined according to the prescribed measuring procedure. The power consumption was determined on the basis of Regulation 692/2008/EC. Power consumption and range depend on the vehicle configuration.
 In addition to charging at a wallbox, the electric smart vehicles equipped with the 22 kW on-board charger with fast-charging function (908) can alternatively be charged at a domestic power socket. The charging time of the fast charger using a domestic power socket is longer than the standard solution owing to the lower efficiency. If you wish to charge your electric smart at a domestic socket in an older building or in the vicinity of industrial plants, we recommend having your domestic socket checked for suitability by a qualified electrician beforehand.
 According to Guideline ECE R85 in the currently valid version.
 Measured according to the New European Driving Cycle (NEDC, ECE R101). The range may be reduced depending on the individual driving style, road and traffic conditions, outside temperature, use of air conditioning/heating, etc.
 The Wallbox design may vary. Please contact your smart dealer for detailed information.