Midi Maping?

hi, im new to midi recording, it took me a while to figure out exactly which controller I wanted so I ended up with the Alesis vi25, I can record notes and chords onto tracks and play drums etc but what I cant do (and this is the reason I bought the controller) is control any of the controls on the vst synths etc or trigger any recorded loops or samples in a track using the 16 pads available on the controller, the manual that came with the model is rubbish and explains nothing, so here we are, I believe I have to manually map the controller in c8 but… I haven’t got a clue, I have watched some videos and they seem to be auto mapping the models in question, and as for alesis ??? utter garbage after sales, so before I send this item back and opt for a lunchkey25 (which is automap) I would really like to give it a shot as I believe this could be an incredible controller if I just got it to work properly, so any advise on how to map this model please?
thank you so much