You can use Qt Creator: Connect your Ubuntu Touch Device through usb open your project and simply press Ctrl+F12
.
This works only if you have once installed ssh-server on the device.
Alternatively you can do it manually. Copy the necessary files (*.qml and *.desktop) to the device and start the application via ssh
qmlscene --desktop_file_hint=/usr/share/applications/qmlscene.desktop YourApp.qml
Source
Remember, this is all beta and if you are not a developer then you won't have much use for Ubuntu Touch at this stage. Eventually, Ubuntu Touch will have its own app store where it will be much easier to download apps and install them on your device.