You may want to look at the document link at the bottom which gives all the examples of how to configure 8.3 NAT onwards. You can download the pictures section separately and it gives specific examples. When you configure with the new NAT you need to configure it all in one because of the way it groups it together in the configuration.
What i mean by this is that you should not reference your existing INT_Net as it would not be grouped with the rest of the specific NAT configuration.
There are basically two ways to configure what you are trying to do but you should read the document because depending on the other NAT on your ASA you might need to use one or the other ie. section 1 dynamic PAT or section 3 dynamic PAT.