Ok, I understood and I solved that problem. Now Forge is installed, but there's another problem: when I try to start the game with my Forge profile, in Shiginima Launcher, it gets blocked after the screen "Mojang" finishes loading Forge and mods, and it takes me back to Shiginima.
I've tried to install Forge 1.7.10 many times, but when I try to install the client always appears a message that says "These libraries failed to download. Try again. org.scala-lang:scala-compiler:2.11.1
Out of memory: Try restarting with JVM Argument: -Xmx1G"
Which is the problem?
I've already tried to set this "-Xmx1G" but, when I opened launcher in "edit profile", I saw this text was already there.