its really not that hard at all.
Create a material.
Import your textures from your computer. start simple. don’t worry about opacity or normal maps yet.
So lets say you have grass dirt and rock, import the image textures into a content folder. then in your new material drag each one into the material. that will create an image texture for you.
Right click and add a Texture coordinates node for each one.
Then right click and create and add a 'layer blend" node. clock on that newly created node and add layers for each and name them.
Make sure they are set to weight blend for now. then from each texture drag from the RGBA into the layer blend for each layer created with the name matches for what each texture is.
Then from the layer blend node drag to the base color of the material.
Now in Unreal go to modes and click on landscape.
Click on your landscape and in the details select the material you created. Now go to landscape panel, Once in landscape click on paint. Once clicked go to the details panel for landscape and scroll down to show materials. For each layer click the plus sign to make a material info file, save for each one.
Start painting.
Checkout a bunch of tutorials for visuals. It will make sense to you soon =) Good Luck!