At the bottom of the window showing your family tree, there is a line starting with an icon of a printer, just above the set of Show/Parents/Children/Others boxes.
To the far right is a link you can click on labeled "Find" followed by the number of people in your tree (e.g. "Find (123 people)".
Click on "Find" and you'll get a selection box with the name of the person currently selected in your tree.
Click on the down arrow (v) on the far right of the box, and the box will expand to show people in your tree, listed alphabetically by Last name then First name, along with birth & death years.
You may need to scroll up or down to find the person you want, then select that person and he/she will then be the center of focus in your family tree window.