The newest build should be included in one of the repositories. Let's suppose that you are using a raspbian system. First you need to update before getting the upgrade.

sudo apt-get update

If you only want to upgrade your systemd version to the compiled newer one available just select it:

sudo apt-get upgrade debian

The newest build should be included in one of the repositories. Let's suppose that you are using a raspbian system. First you need to update before getting the upgrade.

sudo apt-get update

If you only want to upgrade your systemd version to the compiled newer one available just select it:

sudo apt-get upgrade systemd