This command was given by Jesus to Paul when stricken blind on the Damascus Road (Acts 9:1-6). "There you will be told (or find out) all that you have been assigned to do." So Paul was led into the city where he met Ananias. It was through this man's prayer that Paul received back his sight. This was the beginning of a repeated cycle for Paul..."get up and go....get up and go......get up and go."
From there on to the end, the Book of Acts we read of the exciting adventures of Paul as he fulfilled the 'assignments given him' by the Lord Jesus.