Sometimes the Joomla Update component is missing in the Components menu in the backend. A workaround has been to use the extension manager and paste the update package URL and make the update that way.
But when updating to Joomla 3.5.0 that method is not possible. A quick solution, if the Joomla Update component is present but just not displayed in the menu, is to call the URL to the component directly. In the address bar of your web browser, enter:
Now you can do the Joomla version update.
To solve the problem on a more permanent basis (i.e. to get it back into the Component menu in the backend), see this article.