As the driver you put your driver card in slot 1 and use the number 1 button to change activities.
I haven’t watched all through these videos so cannot vouch for the accuracy but be aware that the precise way of doing manual entries may change a bit depending on the version (age) of the VDO.
How to use Siemens DTCO 1381 Digital Tachograph unit PART 1
How to use Siemens DTCO 1381 Digital Tachograph unit PART 2
How to use Siemens DTCO 1381 Digital Tachograph unit PART 3