AWS RDS Error 2003

I am unable to connect to my RDS instance and keep getting

ERROR 2003 (HY000): Can't connect to MySQL server on "my endpoint"

I know that this error comes because my PC is not authorized to access the database because of Public Accessibility, but I am unable to get my PC to authorize in security groups.

I opened the RDS security groups and it says this:

Using VPC? Visit the VPC page to create or manage VPC Security Groups and ingress rules to your DB Instances in VPC. Learn more about the differences between DB Security Groups and VPC Security Groups here.

Your account does not support the EC2-Classic Platform in this region. DB Security Groups are only needed when the EC2-Classic Platform is supported. Instead, use VPC Security Groups to control access to your DB Instances. Go to the EC2 Console to view and manage your VPC Security Groups. For more information, see AWS Documentation on Supported Platforms and Using RDS in VPC.

So I opened VPC security groups and added another security groups with

Type : MySQL(3306) Protocol : TCP(6) and Source as my IP and another for my EC2 instance.

and added this to my RDS security group.

Nothing happened. So I check a tutorial and they added a CIDR/IP and I cannot find that.