Create App Catalog Using Windows PowerShell

Here you go:

New-SPSite -Url http://teams.contoso.com/sites/AppCatalog -OwnerAlias "Contososp_admin" -Name "Contoso App Catalog" -Template "APPCATALOG#0"

Update-SPAppCatalogConfiguration -site http://teams.contoso.com/sites/AppCatalog 

CJG