To get your Instagram Client ID, Client Secret and Access Token follow few steps below...
Copy the URL below and replace the UPPERCASE (red color) with the information you noted earlier on Client ID and Redirect URL (as shown above).
https://instagram.com/oauth/authorize/?client_id=[CLIENT_ID_HERE]&redirect_uri=[REDIRECT URI]&response_type=token
After changing CLIENT ID and REDIRECT URL, paste the full URL in your favorite browser and hit enter.
You will be taken to Instagram server for authorization. Click 'Authorize'
Now you will been redirect to the URL you set as your REDIRECT URL, if you look closely to the URL you will see your Access Token after '=' (equal to sign), something like this...
http://sitename.com/#access_token=85461025.f569f6c.e3cd87a986524862043476fcd1e9463e (this is fictitious access token)
Your access token is like a password for your Instagram account and so shouldn’t be revealed to anyone.