How to pass POST params in HTTP Request?

I’m trying to pass POST params to be read in php form, then I want to execute a php login code based on these params
I’m using this code, what is missing?

void UGameInstanceYU::RequestLogin(FString Login, FString Password)
	TSharedPtr<FJsonObject> JsonObject = MakeShareable(new FJsonObject());

	TSharedRef<IHttpRequest> HttpRequest = FHttpModule::Get().CreateRequest();

	HttpRequest->SetHeader("Content-Type", "application/json");	

	HttpRequest->OnProcessRequestComplete().BindUObject(this, &UGameInstanceYU::OnResponseReceived);


You aren’t actually passing any parameters via the POST.

You should be using one of these functions to pass the parameter data

can you give a small example how to use it with this:

curl -s —user 'api:YOUR_API_KEY' \ \ 
-F from='Excited User ' \ 
-F \ 
-F subject='Hello' \ 
-F text='Testing some Mailgun awesomeness!'