Hi Nordsee,
To measure DC current up 10Amps, you must change the red lead to the connection next to the 10A DC position, then set the range selector switch to this position.
The meter must then be be connected in series with the motor or the circuit being checked.
The most convenient way, normally, is to remove one battery lead, and connect this to one lead of the instrument, then connect the other instrument lead to the battery terminal.
When the circuit is then switched on, the current will be displayed on the meter.
As it is a digtal instrument, the polariy of the connection is not critical, it will simply indicate a -ve figure if connected in 'reverse'.
I hope this helps.
If you have any questions, feel free to pm me.
Peter