You May get the following error “Your organization is not configured to allow access to the Microsoft Dynamics Marketplace web site. To access the website, the marketsettings.InternetConnectionProxyEndpoint attribute must be set to the URL for your proxy server ” when you go to Settings > Customizations > Dynamic Marketplace within CRM.
To set this run the following in PowerShell on the CRM Server
$Setting = Get-CrmSetting -Setting MarketplaceSettings
Get-CrmSetting -Setting MarketplaceSettings
Once you have done this reboot the server as the change will not take effect otherwise and you will be able to access the Dynamics Workplace from within CRM