README: Add installation

README.md

@@ -1,2 +1,26 @@
 # tm - testbed manager
 [![Build Status](https://travis-ci.org/micchie/tm.svg?branch=master)](https://travis-ci.org/micchie/tm)
+
+## Installation
+Assuming the group is set to the users of tm:
+```
+sudo cp tm.py /usr/local/bin/tm
+sudo chmod 754 /usr/local/bin/tm
+sudo mkdir /usr/local/tm
+sudo chmod 775 /usr/local/tm
+```
+In Ubuntu 18.04
+```
+sudo cp tm-cleanup.* /lib/systemd/system/
+```
+In Ubuntu 20.04
+```
+sudo cp tm-cleanup.* /usr/lib/systemd/system/
+```
+```
+sudo systemctl enable tm-cleanup.timer
+sudo systemctl start tm-cleanup.timer
+systemctl start list-timers
+```
+In the UNIT and ACTIVATES rows, tm-cleanup.timer and tm-cleanup.service should
+appear, respectively.