How do I bridge my high and low singing voices?

I'm 16. I play guitar and write songs and sing and such all the time.
I've noticed that the more i practice my singing the higher notes i
can hit. But I can kind of open my throat up more and it's like all
the notes i had access to with my normal voice but like a whole octave
higher. And i just call this my high voice and the other my normal
voice. But i want to bridge the difference. The high voice can hit the
notes but not with as much power or control of vibrato as my regular
singing voice. I want my regular singing voice to be able to hit the
notes my voice can, with the same power and vibrato and just.. idk
ability to get out there loudly and say "HEY F%^ YOU!" Ya know? Just
a powerful voice. So how do i get my voice to stay powerful and bridge
the gap between those two voices? And if you can explain a bit more on
what actually happens when my voices change. The high voice sounds
sort of little girlish.