Copy from Server A (logged on) to B (destination)
scp /path/server/A/source username@serverB:/path/to/destination
Server B to A
scp username@server:/path/to/file /path/to/local/destination
Copy from Server A (logged on) to B (destination)
scp /path/server/A/source username@serverB:/path/to/destination
Server B to A
scp username@server:/path/to/file /path/to/local/destination