How to assign more power to Minecraft?
In the launcher you have "installations" at the top. On there you can see all profiles… If you click on one, you will see the name, resolution, version and path. At the bottom there's "More Options"… There you will also find the Java arguments…
At the launcher on Installations, then click on the version you like, below on more options,
Then there's JVM arguments below, in the line there's something like -Xmx2G-
2G stands for 2 gigabytes of RAM. You change this number as you like.
But consider how much RAM your PC can provide.