How use and configure Mprint?

I was tried to print using mprint on mbot cube ll dual head, but only can configure for the right extruder, if i want to select the other extruder need to change the filament, additionally, when print a piece lika a cilinder with a close trajectory leave a mark at the beginning and the end, could some one advise me?

Regarding MPrint; You need to select the extruder before export file into x3g. Otherwise, right extruder will ok as defult extruder.
Mark at the begining and end; It seems two extruder are not parallel. You can check this link for adjustment. If still problme then contact us at [email protected]

Tried to connect with my iPhone but it showed up incompatibility with the device. I then downloaded a driver for setting up the connection from apple customer service but the attempt was not successful