not sure about your model, but the usual way is to go into settings..keyboards and choose your virtual keyboard.
Then go into an app like messenger. Long press on the space where you enter text and a pop up will come around and ask you what input method you would like to use...
My model is ChaCha, in settings I only have Touch Input parameters, I can't choose a virtual keyboard even if I install a 3rd party virtual keyboard and enables it as default, it doesn't show up ...