ing and ed in interest and excite

-ing

We use the -ing form of interest to talk about the
subject. 
For example:

1. When I was in Oz I met so many interesting people.
2. The road trip to the outback was exciting.
3. Darling Harbour is an interesting place to visit.
4. I had an exciting time in Melbourne riding bicycles.

-ed

We use the -ed form of interest to talk about how people
feel. 
For example:

1. I’m interested in Australian history.
2. Doni was excited to go on a tram around Sydney.
3. I’m interested to go to Oz to see Uluru.
4. He was excited to see the koalas at the Australia Zoo.

Good luck learning English!