First of all you should know that this is a sensitive subject. Very few people are willing to admit that they have a problem. Especially if they are at an early stage of their addiction. You have to be careful not to create a confrontation that can damage your relationship permanently.
First off all it is important to know that your friend does not necessary have a gambling problem just because he gambles a lot.
If you still think your friend has a gambling problem then you should start by protecting yourself and make sure that the gambling does not have a negative effect on your life. Do not lend your friend any money and do not get roped into the gambling.
Once you have protected yourself you can start helping your friend. Before you do it is important that you understand that you might not be able to help him. You can not help your friend if he doesn’t want to be helped. Sometimes you have to wait until they are ready to change.
Contact a help organization in your local area to get more advice on how to help your friend. They will be able to give you advice based on your specific situation. They will also be able to tell you how your friend can get help in your local area.