Can't Setup NAT For Linux Device?

I am having a problem configuring NAT for a Linux device on our network. I am far from a Cisco expert but I have configured this many times in the past for Windows machines quite easily. I do this using the Cisco ASDM 5.2 for PIC GUI. All I needed to do for the Windows machines was:-setup the static NAT rule(inside ip translated to outside ip)-create a security policy(outside, incoming rule) to allow traffic to the outside ipand hey presto it works, ie: i can ping the outside ip and access the device remotely if I have allowed correct ports.I am not sure if this is the correct method but it was how i was shown and has worked many times in the past.But with this Linux device its no dice. The Linux device isnt a desktop but a mediator for industrial air conditioning controls. It runs a web server which we can view temperatures etc... through a browser. This works inside our network by browsing to the inside ip but I am trying to set it up to work outside of our network.