bcp YourDatabase..YourTargetTable in c:\YourDataFilePath -c -T -SYourServerName
bcp YourDatabase..YourSourceTable out c:\YourOutputFilePath -c -T -SYourServerName
These are just basic examples for importing/exporting a basic tab-delimited text file. Like rmaio said, look into Books Online for further explanation, or type bcp -? from the command line.
What if I have another instance eg. Server\instance_name? because the reply was "ct_connect(): directory service layer: internal directory control layer error: Requested server name not found."