To update to the latest 5.5 image profile directly from the VMware online repository (requires internet access for the host) do this:

# esxcli network firewall ruleset set -e true -r httpClient

# esxcli software profile update -d https://hostupdate.vmware.com/software/VUM/PRODUCTION/main/vmw-depot-index.xml -p ESXi-5.5.0-20151004001-standard

If your ESXi host does not have direct internet access, then download the ESXi 5.5 Update 3a Offline Bundle from here and upload it to the host:

https://my.vmware.com/group/vmware/details?downloadGroup=ESXI55U3&productId=353&rPId=9553

Then apply the update with:

# esxcli software vib update -d "/full/path/to/offline/bundle.zip"

Also see:

VMware KB: Installing patches on an ESXi 5.x/6.x host from the command line

Both methods will update every ESXi package on host to the latest version.