Requirements

Knowledge of FTP
CuteNews installed

Make sure you have the smileys you want saved in your computer somewhere. Otherwise how else will you replace them?
Now, there are two ways you can do this. Either 1)upload the smileys overwriting the default, or 2) add your own amount. Each way will be shown here.

1. Log-into FTP and go to your CN folder. Inside you will find several folders like data, inc and skins.
Click on the data folder and inside you will see four subfolders. Click on emoticons. You should now see all the emoticon images.
I doubt the emoticons on your computer had the same names as these, so re-name them to the names in the folder, and overwrite.

2. Log-into FTP and go to your CN folder. Inside you will find several folders like data, inc and skins.
Click on the data folder and inside you will see four subfolders. Click on emoticons. You should now see all the emoticon images.
You can delete those, and instead upload your own. Suppose I uploaded the names hamu1.gif, hamu2.gif and so on..
Once done, log-into CuteNews and click Options>>System Configurations. The fifth thing you should see would be smileys. It would say something like
Smilies Separate them with commas (,)
Beside that there will be a box with the names of all the smileys. What you simply do is delete the ones there and add your own. As I've said, I supposedly added the emoticons with the names hamu1.gif and hamu2.gif. What I would do now is add these instead.
You should write something like hamu1,hamu2 the way you see it. (simply adding the name of your smileys except the file format. Make sure there are no spaces between each thing)

That's it! I hope you have a fun time updating with your new emoticons.