So if you need to restore your contacts:
1) Open Mail app on your device (iPhone, iPad or iPod touch)
2) Find the message including backup file sent previously to yourself
3) Tap on the attachment named (MyContactsBackup*.vcf)
Important: You can’t restore your contacts from CSV files same way. CSV is not a backup a file, it’s just an export file. You need to convert .CSV file to .VCF file first.