You can use KnowledgeTree's sharing capabilities through the KnowledgeTree tab in Salesforce.  This can be used when you aren't working in a particular Salesforce object such as Opportunity or Lead, but know who you want to share content with quickly.

You must have contacts or leads assigned to you to be able to share content using this feature. 

To find the KnowledgeTree tab, click on the + in the main navigation bar of Salesforce.

You can also add KnowledgeTree to your default display by customizing your tabs.

Once you are in the KnowledgeTree tab, as a sales users you will see the Share screen in which you will notice your most recent Items on the left of the screen and all published assets in the middle.

You can search for a person under recent Items on the left. 

By clicking on one of the contact names, you will be taken to a screen with recommended content that you can then share as you normally would using KnowledgeTree.

Under "All Published Assets" you can download, preview and share just as you normally do by using the icons to the left of the asset title. 

Under the sharing dialogue - you will be given the full list of your available contacts.

You can also filter "All Published Assets" list by tag to find the content you are looking for.