Call post api from interface

Hi, 

i've a portal with some users fileds. When i compile the fields on click button i want to save this fields in my appian db using post api (i want to test the API). I wrote this code for the portal interface:

_{=a!localVariables(
local!nome,
local!cognome,
local!dataNascita,
local!indirizzoResidenza,
local!codiceFiscale,
{
a!textField(
label: "Nome",
value: local!nome,
saveInto: local!nome
),
a!textField(
label: "Cognome",
value: local!cognome,
saveInto: local!cognome
),
a!textField(
label: "Data di nascita",
value: local!dataNascita,
saveInto: local!dataNascita
),
a!textField(
label: "Indirizzo di residenza",
value: local!indirizzoResidenza,
saveInto: local!indirizzoResidenza
),
a!textField(
label: "Codice fiscale",
value: local!codiceFiscale,
saveInto: local!codiceFiscale
),
a!buttonLayout(
primaryButtons: {
a!buttonWidget(
label: "Invia dati",
saveInto: {
}
)
}
)
}
)}

I also created a post api:

a!localVariables(
local!value: cast(
'type!{urn:com:appian:types:AHUTENTE}AH_UTENTE',
a!fromJson(http!request.body)
),
a!writeToDataStoreEntity(
dataStoreEntity: cons!AH_UTENTE_DSE_POINTER,
valueToStore: local!value,
onSuccess: a!httpResponse(
statusCode: 200,
headers: {
a!httpHeader(name: "Content-Type", value: "application/json")
},
body: a!toJson(
fv!storedValues
)
),
onError: a!httpResponse(
statusCode: 500,
headers: {
a!httpHeader(name: "Content-Type", value: "application/json")
},
body: a!toJson(
{
error: "There was an error writing to the data store"
}
)
)
)
)

Now I was wondering, how do I call the API to write to the db within the interface and pass the parameters? Do I need anything else? Sorry but I'm not very practical.