MultiMC modpack installation
Download MultiMC here.
Open MultiMC and click on Add Instance to create a new instance.
Then select Minecraft version 1.18.2 and name the instance whatever you want.
On the main MultiMC window you'll now see your new instance. Click on it once to select it, and on the right side panel click Edit Instance. This new pop-up window is where you can configure this instance. From inside the pop-up window, click Install Forge and be sure to select version 40.1.84, then click OK.
With Forge installed you can now go to the Loader Mods tab (on the left side). Download the ZIP file from the IceDrive link in the README. Open it and select all the mod jar files inside. Drag them to the empty Loader Mods screen and you will see it populate with all the mods you dragged in.
Now you should be able to launch the game and join the server. But for a large modpack, you should allocate at least 4GB of RAM (preferably more). To do this in MultiMC, click the Settings tab of the instance pop-up window and check the Memory box to edit the minimum and maximum memory allocation. Set the amount of ram in megabytes (MiB). So for 4GB you would set both boxes to 4096 MiB (number of GB x 1024).