Here's a comprehensive guide:
Method 1: Syncing Contacts from Your Phone's telegram number database Address Book (Automatic)
This is the most common and easiest way to find friends already on Telegram if you have their phone numbers saved in your device.
Enable Contact Sync in Telegram:
Open the Telegram app.
Go to Settings (on Android, tap the three horizontal lines ☰ in the top-left; on iOS, tap the gear icon
Tap Privacy and Security.
Scroll down to the Contacts section.
Make sure the "Sync Contacts" toggle is ON (it should be blue or green and on the right side).
Grant Telegram Permissions to Your Phone's Contacts:
Telegram needs permission from your device's operating system to read your contacts.
For Android:
Navigate to Apps (or Apps & notifications, App management, depending on your phone's model).
Find and tap on "Telegram".