This article explains how to see who added you on Snapchat.
Steps
Step 1. Open the Snapchat application
Its icon depicts a white ghost on a yellow background.
If you are not already logged in, tap "Login" to enter your username (or email address) and password
Step 2. Swipe down on the main screen
This will open your profile.
Step 3. Tap They added me
Step 4. Look for the phrase "Added me" under a username
If the person you added to your friends list has reciprocated, under their username you will see their name, username and the phrase "Added you". You'll also see an emoji and the option to snap her or chat with her.
Step 5. Look for other names in the "Added me" menu
The usernames of all the people who added you as a friend will appear in this section, whether you added them first or not. The phrase "Added you by username" or "Added you by snapcode" may appear under their names.