Try initializing the variables with values according to you particular situation like set HOST,USER,etc to their respective correct values.
#!/bin/sh
USER=login_of_user_on_remote_system_that_can_access_logs
HOST=host.name.of.remote.host
LOG_DIR=/absolute/path/to/where/the/log/file/is/
FILE=name_of.log
DESTINATION_DIR=/where/to/save/log/on/local/host/
scp $USER@$HOST:$LOG_DIR/$FILE" $DESTINATION_DIR