Add the SharePoint sites to the Local Intranet zone or to the trusted sites zone on the Internet Explorer browser.
Open Internet Explorer and click Tools > Internet options.
In the Security tab, click Trusted sites > Sites.
Specify the SharePoint site URL and click Add.
Click Close.
IMPORTANT:To enhance the security, enable the following options in the browser:
Go to Tools > Internet Options > Advanced, and then select Empty Temporary Internet files folder when browser is closed under Security.
Go to Tools > Internet Options > General, and then select Delete Browsing history on exit.