Here's the process for importing vCard contacts (you'll sometimes see a filename ending in .vcf) into Gmail.
1. Log into Gmail
Log into your Gmail account as normal.
2. Select "Contacts", then "Import Contacts"
Click "Contacts" near the top-left of the Gmail window. Then select "Import Contacts".
3. Select your vCard or .vcf file
Click "Choose file" and choose the vCard or .vcf file containing your contacts.
That's it! Your contacts should now be imported.