It's easy to get started using Evernote for Salesforce:
Create an Evernote account to link only your own notes, or get Evernote Business for your company to allow your team to share knowledge and collaborate.
If your business doesn't already have a Salesforce.com account, create a Salesforce.com account for your business. Evernote for Salesforce is available at no additional cost for customers using Salesforce.com's Group, Professional, Enterprise, Unlimited, Force.com, or Developer editions.
An administrator for your Salesforce account will install the Evernote for Salesforce managed package. See the Evernote for Salesforce Installation and Administration Guide for installation details.
Once you have Evernote for Salesforce installed, you can start using Evernote to create notes and link them to your Salesforce records.