How to create custom clone button with product for Salesforce opportunity sobject?

VF Page:

<apex:page standardController="Opportunity" extensions="oppExtension" tabStyle="opportunity">
<apex:form>
<apex:pageBlock title="Opportunity Edit">
<apex:pageBlockButtons >
<apex:commandButton action="{!save}" value="Save"/>
<apex:commandButton action="{!cancel}" value="Cancel" immediate="true"/>
</apex:pageBlockButtons>
<apex:pageBlockSection title="Opportunity Information">

<apex:inputField value="{!OpportunityCloned.owner.name}" label = "Opportunity Owner"/>
<apex:inputField value="{!OpportunityCloned.amount}"/>
<apex:inputField value="{!OpportunityCloned.isPrivate}"/>
<apex:inputField value="{!OpportunityCloned.CloseDate}"/>
<apex:inputField value="{!OpportunityCloned.name}"/>
<apex:inputField value="{!OpportunityCloned.NextStep}"/>
<apex:inputField value="{!OpportunityCloned.Accountid}"/>
<apex:inputField value="{!OpportunityCloned.StageName}"/>
<apex:inputField value="{!OpportunityCloned.Type}"/>
<apex:inputField value="{!OpportunityCloned.Probability}"/>
<apex:inputField value="{!OpportunityCloned.LeadSource}"/>
<apex:inputField value="{!OpportunityCloned.Campaignid}"/>
</apex:pageBlockSection>
<apex:pageBlockSection title="Additional Information">
<apex:inputField value="{!OpportunityCloned.OrderNumber__c}"/>
<apex:inputField value="{!OpportunityCloned.MainCompetitors__c}"/>
<apex:inputField value="{!OpportunityCloned.CurrentGenerators__c}"/>
<apex:inputField value="{!OpportunityCloned.TrackingNumber__c}"/>
<apex:inputField value="{!OpportunityCloned.DeliveryInstallationStatus__c}"/>
</apex:pageBlockSection>
<apex:pageBlockSection title="Description Information">
<apex:inputField value="{!OpportunityCloned.Description}"/>
</apex:pageBlockSection>
</apex:pageBlock>
</apex:form>
<apex:relatedList list="OpportunityLineItems" />
<apex:relatedList list="OpenActivities" />
<apex:relatedList list="ActivityHistories" />
<apex:relatedList list="CombinedAttachments" />
<apex:relatedList list="OpportunityContactRoles" />
<apex:relatedList list="OpportunityPartnersFrom" />
<apex:relatedList list="OpportunityCompetitors" />
<apex:relatedList list="OpportunityHistories" />
</apex:page>

Apex class:
public class oppExtension {
private ApexPages.StandardController controller {get;set;}
private opportunity opp{get;set;}
public Opportunity OpportunityCloned {get;set;}

public oppExtension(ApexPages.StandardController controller){
this.controller = controller;
opp = (Opportunity)controller.getRecord();
opp = [select Id,owner.name,Accountid,Amount,CloseDate,Contractid,Description,OrderNumber__c,MainCompetitors__c,
CurrentGenerators__c,LeadSource,NextStep,Name,stageName,Ownerid,Campaignid,IsPrivate,Probability,
Type,DeliveryInstallationStatus__c,TrackingNumber__c from Opportunity where id =: opp.Id];
OpportunityCloned = opp.clone(false,true);

}
public PageReference save() {
try {
insert(OpportunityCloned);
} catch(System.DMLException e) {
ApexPages.addMessages(e);
return null;
}
// After successful Save, navigate to the default view page
return new PageReference('/'+OpportunityCloned.id);

}

}