Add a short instruction about environment variables.

README.md

@@ -79,6 +79,24 @@ make install
 ```
 Depending on where you are installing the monitor, you may need special permissions.
 
+If you install the monitor under the location you specified, you may need to set the environment variable `PATH`.
+Otherwise, you have to enter the full path to the executable when you execute the monitor.
+In the case of Linux system, the recommended way is to add the following line at the bottom of `~/.profile`:
+```
+PATH="YOUR_INSTALLATION_DIR/bin:$PATH"
+```
+Then, log out and log in again.
+
+You may also need to set the library path before executing the monitor.
+In most Linux systems, you can modify the library path by editing `/etc/ld.so.conf` or the environment variable `LD_LIBRARY_PATH`.
+The recommended way is to use `LD_LIBRARY_PATH` because all users can edit this variable without extra privileges.
+Add the following line at the bottom of `~/.bashrc`:
+```
+LD_LIBRARY_PATH="YOUR_INSTALLATION_DIR/lib:$LD_LIBRARY_PATH"
+export LD_LIBRARY_PATH
+```
+Then, open a new terminal.
+
 ## :wastebasket: Uninstalling
 In the case of autotools, the monitor can also be easily removed by entering the distribution directory and running
 ```bash