What is the best way to connect two power wires together.I bought a kit with a 14' 4 ga. power wire but I don't think it's going to be long enough.What is the best way to connect another 10' length.And should it be the same brand.

salder

solder

So you mean solder the two ends together then cover with shrink tubing.Sorry, I have almost no experience in this field but am very mechanically inclined.My best suit is woodworking not electrical.

I would think if you were adding less than 5', you could just put your inline fuse in at that point. But for 10', I guess soldering is the way.

Burndy butt splice connector, hydraulic crimper. or, if U have access, 2 4 guage lugs, or crimp on ocnnectors, and a both through the 2 of them to connect them, then heat shrink, or tape them together.

buy the right legnth of wire, or the fuse teqnique i guess, i would never recommend soldering 4 awg, pretty cheesy

^^ Ditto
That and to do a proper solder on 4 awg you will need a lot of heat. You would need a professional grade solder gun (which I assume you don't have because woodworking is your forte).

You could also use Copper Brake line, a peice about 1" long in size, Crimp together (I use vice grips with that big of wire) then insulate it with vinyl/tape.

copper is way too weak for brake lines, it'd rupture. but copper tubing might work.