connecting water supply to inlet of electric shower?

[diditmyself]

the new shower has options of two inlets, both plugged. one of the plugs has to be removed (obviously) and this is easily done as both plugs are push fittings. My question is, is it simply a matter of pushing 15m copper pipe into the same inlet after the plug has been removed? I have push fittings under my kitchen sink and these appear to be similar?