Among other things, Powershell 2.0 doesn\'t have the useful cmdlet Invoke-RestMethod.
I can\'t upgrade to version 3 and most examples I\'ve found
From curl's man page it appears you need to use -d switch:
-d
curl -v --user username:password -H "Content-Type: application/json" -d '{"Id":5,"Email":"test@com","DataFields":null,"Status":0}' https://api.dotmailer.com/v2/contacts