Hi,
If you’re using one of the editions listed above and would like the AppExchange enabled for your organization, have a system administrator open a case with Salesforce Support and include the following details:
1. On your case, specify AppExchange Download and AppExchange Upload.
2. Include your ID of the production or sandbox organization where you would like this enabled (under Setup | Company Profile | Company Information).
Request for ‘AppExchange Download’ to download applications.
Request for ‘AppExchange Upload’ to upload both Public and Private packages to AppExchange.
Our Support team will review your request and take action.
Hope this helps.