See instructions for your platform.
The easiest way to get wapm is to get the current stable release of Wasmer by using the install script:
curl https://get.wasmer.io -sSfL | sh
This will get you the current stable release of Wasmer for your platform along with the latest wapm.
Use the wasmer installer on the releases page to install wapm-cli
.
Alternatively, you can build wapm from source.