Creating app for accessing apis

Hi samadhan dhangar. I'd recommend starting with the REST API documentation, which covers authentication and making REST requests. Let me know if you have any specific questions.

When i call any rest api i need to use username and api key,

so is this the username of app created ?

when i try the same with my username it does not work.

I'd recommend using OAuth instead, as shown in the API documentation.

That said, if you prefer using user name and key, you can still do that as well. Log in as the user in your community that you wish to access the API as, navigate to the user's settings > API Keys > Manage application API keys. There, you can create a new key. Then your user name is the same user name you're logged in as, along with the key you just created.