Well, basically iMovie titles are not able to be repositioned. There are titles that have the text displayed in different parts of the screen, but you are stuck with the template that determines the position.
Here's what I do for a workaround: Take a duplicate of any random photo and open it in the Preview app on your Mac. Do an Edit/Select All, Edit/Delete. That will leave you with a blank transparency screen. Then, in Preview, go to Tools/Annotate/Text. You then can type text into a text box onto the transparency screen. You can create as many text boxes as you want. In the toolbar at the top of the Preview screen you can select your text font, size, and color. After typing your text title save it to your desktop. Then import it into iMovie. Place it in the upper timeline, and overlay it onto whatever clip or background in which you want to insert your title. Select the title clip by clicking on it. Then go to the toolbar in the upper right of your screen and click on the overlay icon (the one that looks like overlapping squares). Choose Picture in Picture from the selection box that appears. The title clip will appear on the preview screen overlaid onto the clip below. Adjust the size and position of the text on the preview screen by dragging. To set the size you can drag a corner completely off of the screen. Then click on the blue reset button to apply your PiP settings. That will overlay a title onto the clip below it in any position and size that you want.
Sounds complicated but actually is very easy once you have done if for the first time. Also, creating a transparency screen can be very helpful for inserting logos or other clips onto the main clip below.
-- Rich