Update README.md

Improve configuration section and add building from source section

README.md

@@ -4,7 +4,14 @@ An application to upload a file or perform a command on multiple servers via ssh
 
 ## Configuration
 
-Set the environment variable `MSSH_SERVERS` to configure the server directories of your ssh servers
+Set the environment variable `MSSH_SERVERS` to configure the server directories of your ssh servers.
+Furthermore, ensure that in your shell the following commands are set up and working:
+- ssh
+- scp
+- ssh-agent
+- ssh-add
+
+Ergo you should be able to connect to your desired servers via ssh and be able to start an ssh agent.
 
 ### Linux example
 
@@ -50,3 +57,13 @@ For detailed usage of the upload feature see
 ```bash
 multi-ssh -u --help
 ```
+
+## Building from source
+
+This is a rust project so you will need [rustup and cargo](https://doc.rust-lang.org/cargo/getting-started/installation.html).
+
+Once you have that installed, just run
+```bash
+cargo build --release
+```
+and you will find an executable in `target/release`.