It sounds like you want to know how to configure NAT. By "terminal" do you mean accessing the 828 via the command line interface ? If so this will probably be the most difficult way for you to configure port forwarding if you are not familiar with Cisco. You need to know how to get around the CLI interface. But if you know some basics this link will help you.
This feature should already be enabled on your router. All you need to do is go to a PC on your network and open up a web browser like IE and type in the ip address of your 828 (your PC's default gateway address most likely).
Once connected you will be prompted for a username and password the default is no username is specified but in the password field type in the enable password of your router.
Once logged in its a GUI so you should be able to follow the steps and hopefully get things going.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...