First please make sure that routing is OK between PC and i.MX. If they are in the same segment of LAN (usual case) you need to make sure that IP addresses are in the same subnet (for example 192.168.0.2 and 192.168.0.3) and this subnet is added to routing table.
Then please make sure that you can ping one host from another.
If all above is OK you need to make sure that ssh server is running on i.MX. You can check if some server listens to post 22 this way: # netstat -na|grep LISTEN And then you can try to connect ssh from the board itself: # ssh localhost