Minor fixes
Corrected a typo and added `apt-get update` as `/var/lib/apt/lists` is erased during the build of the jenkins image.
diff --git a/README.md b/README.md
index 7e16f94..0eabdbc 100644
--- a/README.md
+++ b/README.md
@@ -82,12 +82,12 @@
# Installing more tools
-You can run your container as root - and unstall via apt-get, install as part of build steps via jenkins tool installers, or you can create your own Dockerfile to customise, for example:
+You can run your container as root - and install via apt-get, install as part of build steps via jenkins tool installers, or you can create your own Dockerfile to customise, for example:
```
FROM jenkins
USER root # if we want to install via apt
-RUN apt-get install -y ruby make more-thing-here
+RUN apt-get update && apt-get install -y ruby make more-thing-here
USER jenkins # drop back to the regular jenkins user - good practice
```