Open the Minecraft Launcher
Go to Installations
Select your Minecraft profile
Click More Options
Find the JVM Arguments box
Change the value after `-Xmx` to the amount of RAM you want
Example: `-Xmx4G` gives Minecraft 4 GB of RAM
Save the profile
Launch Minecraft
If using the CurseForge app
Open the modpack settings
Find Memory Settings
Increase the allocated RAM
Save the changes
If using the Technic Launcher
Open Launcher Options
Find Java Settings
Adjust Maximum Memory/RAM
Save the settings
Do not allocate all of your system RAM
Leave enough RAM for your operating system and other programs