3 Pc with windows (v10, 7 and 8.1), 1 smartphone with android.
How can I proceed ?
please try to explain simply, I'm not a technical man, i'm just a bitcoin user but don't understand everything inside.
Very simple: create a wallet on one pc, write down the seed.
On the second pc, don't create a new wallet, but restore an old one (use the same seed)
idem dito on the thirth one
idem dito on the smartphone (altough, i have never tried this one myself, it should work)