Making meshes is absolutely you learn do just on a day, it require some know how. Many people in this community seem to use the program "Blender" For their mesh making. Other software probably works as well. But without a certain software that can't make these you're stuck already.
There's tutorial vids and other sites that learn you how to do these. As long as you got the will to actually learn you might catch a few things up here and there.
You open rars with a program called "winrar" this is free to download so you can just google it. It's rather easy to use and similar to extracting a zipped file.
Just install winrar, right click the rar file and choose extract here or extract to and your files you work.
