Improve README.md

[hdvos]

Summary

There was a grammatical error in this readme, also the installation procedure was not obvious. For this reason, I made two minor suggestions.

This PR can be summarized in the following changelog entry:

• Corrects a grammatical error in the readme.
• Adds installation instructions to the readme.

Relevant technical choices:

• -

Test instructions

This PR can be tested by following these steps:

• -

Fixes #

[marinakoleva]

CR has been done by @FAMarfuaty and there's no need for testing so I'm merging this issue