Creating a Proxy on a EC2 and accessing it from another EC2

I have created a proxy server on a EC2 XXXX using tinyproxy using following steps :

Connect to your instance using the key pair you downloaded:
ssh -i ~/.ssh/xxxxxxx.pem ubuntu@ec2-XX.XX.XX.XX.compute1.amazonaws.com

Install Tinyproxy
sudo apt-get install tinyproxy

Also updated the conf file and add IP Address of another EC2:

sudo vi /etc/tinyproxy.conf
Allow Ip_another_Ec2/32

From Another EC2 called YYYY, i started the Tunnel on a screen session:

ssh -L 3128:localhost:8888 -N -i ~/.ssh/xxxxxxx.pem ubuntu@ec2-XX.XX.XX.XX.compute1.amazonaws.com

Question:

1. How can i access internet from EC2 YYYY using this proxy running on XXXX.