Installing Terraform is quite simple, since it is written in Go, just download the archive with the binary file.
Go to the download page:
https://www.terraform.io/downloads.html
Download the archive, extract the binary file and move it to "/usr/bin/" (or write it to PATH)
Check:
terraform --version
If you use the "bash" or "zsh" shell, you can add autocompletion for Terraform with the following command:
terraform -install-autocomplete