Where can I use Esperanto?
Mostly the internet, like reddit, twitter, facebook, youtube, telegram, etc. You can find a lot of books in Esperanto too, my favourite is the Hobbit in Esperanto. You should also check to see if your country has an active Esperanto Association or just some groups for meetups. There's also the World Esperanto Congress every year. I learn Esperanto with a friend, it's really fun to use at university or if we go for coffee.
Tell us more about how you want to use it.
In the meanwhile, watch Esperanto Variety Show https://www.youtube.com/channel/UCXnT_KZNsQw-MX8Q8gJQDgw