Hello Shawn and welcome!
Here's a quick list of what you will need. Of course there are many ways to do this, some work better that others and what works great for someone might not work at all for you. You really need to research, which is why you are here!
1) A DSB (deep sand bed) about 4-6 inches of sugar sized sand. Playsand works just fine.
2) Live Rock. There are many choices...Florida, Figi, Tonga,...all are different and you need to pick the type you like.
3) A Protein Skimmer. Some don't use one, some swear by them. Again, it's up to you to decide what's best for you.
4) Circulation. Power heads to move water around.
5) A heater.
6) Salt to make salt water. There are different brands, everyone has their favorite...I recommend Instant Ocean.
You could use the filter you already have, but filters tend to produce too high of nitrate levels for marine tanks. If you want to keep an anemone with your clowns, high nitrates will be a problem. Keep reading and reading....and good luck!