Subscription Settings Service Application and the proxy are two of the prerequisites for developing SharePoint Add-Ins (SharePoint Apps). But this service application cannot be provisioned through the UI. A Subscription Settings Service Application can be created only through PowerShell and below is the script to provision the Service Application and its proxy.
Change the Display Names and Account details as per your environment in the below script and run it through SharePoint Server 2013 Management Shell (opened as a Farm Administrator)
Update these values as per your environment
$login = Get-SPManagedAccount RAMS\ram-svc
$AppPoolName = "SubscriptionServiceAppPool"
$SAName = "Subscription Settings Service Application"
$DBName = "SubscriptionSettingsDataBase"
#Create a New Application Pool
$appPool = New-SPServiceApplicationPool -Name $AppPoolName
#Provision a New Service Application
$serviceApp = New-SPSubscriptionSettingsServiceApplication
-ApplicationPool $appPool -name $SAName -DatabaseName $DBName
#Create a Proxy
$serviceAppProxy = New-SPSubscriptionSettingsServiceApplicationProxy