How to do a POST or UPDATE on restful api server - rest

Question

I'm currently building a restful API server for my mobile devices to access a mySQL database. The mobile apps need to be able to get data from the server, and also insert and edit data.
I have managed to successfuly do a GET from the server, but I'm stuck at how to get do the post. On the WebModuleUnit I added an action, with the following properties:
MethodType mtGet
Name actImsDocuments
PathInfo /imsDocuments
procedure TWebModule1.WebModule1actImsDocumentsAction(Sender: TObject;
Request: TWebRequest; Response: TWebResponse; var Handled: Boolean);
var
qryDocuments: TFDQuery;
JsonArray: TJSONArray;
JsonObject: TJSONObject;
begin
// Configure response
Response.ContentType := 'application/json; charset=utf-8';
//Search for my clients table
qryDocuments := TFDQuery.Create(nil);
with qryDocuments do
begin
Connection := FDConnection1;
Active := false;
SQL.Clear;
Open('SELECT * FROM ims_document');
if qryDocuments.RecordCount > 0 then //if there is items
begin
JsonArray := TJSONArray.Create;
try
First;
while not EoF do //Iterate all items in the FDQuery
begin
JsonObject := TJSONObject.Create;
AddFieldsToJSON(JsonObject, qryDocuments);
JsonArray.AddElement(JsonObject);
Next;
end;
finally
Response.Content := JsonArray.ToString;
JsonArray.DisposeOf;
end;
end;
end;
end;
procedure TWebModule1.AddFieldsToJSON(AJsonObject: TJSONObject;
AQuery: TFDQuery);
begin
with AQuery do
begin
AJsonObject.AddPair('number', TJSONNumber.Create(FieldByName('number').AsInteger));
AJsonObject.AddPair('document_title', FieldByName('document_title').AsString);
end;
end;
Now this all above works perfectly, what I have no idea how to do, is how do I for example, edit a record in the table, or insert a new record, how do I get the values from the mobile device. I have no idea how to do a post, or update. Can anyone just give me an example of code please, as I have looked everywhere and just cannot get a clear understanding of this.
If I change the property of the action to mtPost, how would my code differ If I wanted to add a record to the table?