Add to Chrome.
Click 'Add extension' above.
The installation process should take less than a minute.
Next, you'll Create an Account.
If someone malicously put a keystroke recorder on my computer would they be able to see the master password for LastPass when I enter it?
Yes, they could record your master password, unless you're using the online keyboard: https://helpdesk.lastpass.com/your-lastpass-icon/loggin-in/#h2 for more information.
Another option is multifactor authentication.
Even if someone grabbed your master password, the second authentication method would prevent them from gaining access to your account.