Are you wanting to mount this from the service console, or with the vmkernel (to use as a VM datastore). If this is for service console use, then you'll first need to go to Configuration \ Security Profile, and then click on Properties and enable the NFS client.
From my esx server I want to mount to a linux nfs server (not esx). I have allowed nfsclient in VI but when i try to mount it freezes.
there is no firewall enabled on the nfs server
mount -t nfs nfsserver:/nfs /mnt/nfs
it just freezes
if you want storage for vm use vmkernel wizzard to add storage
if you want just to copy some ISO , VMs then you can try
scp root@IPADRESS:/mnt/volumes/someiso /vmfs/volume