In Sales Connect, click the gear icon on the upper-right and select Settings.
Under Admin Settings, click Salesforce.
Verify you are connected to your Salesforce account.
If you are connected, you'll see a green "Install" button. DO NOT click this button, proceed to step 4 instead.
Log-in to the Salesforce account you are connected to and then click this link.
You'll be sent to the Sales Connect Installation page.
Choose the users you would like to install customizations for: Admin only, all users, or specific profiles.
Click on the Install button to install customization.
To confirm successful installation, log-in to your Salesforce account.
Click Setup, search for "Installed Packages" in the search bar, and click Installed Packages.
You will see Marketo Sales Connect Customizations there.
In order to configure Sales Connect in your Salesforce instance, please follow the steps starting from "CONFIGURING THE SALES ENGAGE SALESFORCE PACKAGE" section on page 7 of the Installation Guide.
Sales Engage is the previous name for Sales Connect.
Installation Guide for Salesforce Classic
Installation Guide for Salesforce Lightning