If you are parsing a chat message
You would parse the tags of a chat message for the emotes object.
Which’ll give you the emoteID and the places in the string for that emote
Then you can construct the URL to the image
https://static-cdn.jtvnw.net/emoticons/v1/emoteID/1.0
You can substitute 1.0 for 2.0 and 3.0 depending on what size you want.