We have forwarded an older domain to our new NetSol ecommerce domain, but I just read about the 301 redirect should be done in order to keep the SEO placement. Does anyone know how this can be done. Both domains are hosted by NetSol. Thanks!

If your Domain name is assigned to the ecommerce package in your Network Solutions Account manager, it automatically does a 301 redirect to the primary domain name.

Our old domain was not an ecommerce site w/ NetSol -- it was with another host.

That is fine, if the domain name is already pointed at your ecommerce package just go into your account manager and add it to the ecommerce package as a secondary domain by going Ecommerce>>Manage Ecommerce and clicking the Assign Domains button. If the domain name isn't pointed yet you can still assign it, but after you would just need to point it to the Ecommerce package by entering ethier the NetSol name server, a CNAME record or an A record, found in the view DNS link in the Manage Ecommerce Domains area of your Account Manager, into the DNS settings of the domain name's Registrar.