you didn't do anything wrong in your last post but you were about to.if i hadn't said anything i think you would have released the models & ended up getting a ban.
there is nothing wrong with using a program like mixamo to make characters for your game its no different than using one of TGCs model packs.the problems come if you try to claim them as your own work or distribute them in a model pack or on there own.
its always best to make all your own media, that way you can do what you like with it without fear of comebacks.remember if you can find it on the net so can everyone else.
you are new to game media creation so start simple & take your time look for tutorials on modelling texturing etc & work your way through them (there is a lot to learn but if you work hard you will get good results)
good luck
cheers henry