How can I add another project to my project?

I want to use LandscapeMountains project and assets in my project but I could not exactly add this project to my project. I am adding but some materials are not working. I wonder how can I add this project to my project exactly?

You can Migrate Assets. It’s in the right-click drop-down menu in the Asset Actions section.

As @Tuerer said, you can use migrate functionality. Read more here: Migrating Assets | Unreal Engine Documentation

Finaly I made it and all assets work good thank you.

I made it thank you.