Please have a look at the interactions tutorial on the website if you want the user to be able to scroll/drag the plot. If you want to do it automatically, have a look at the documentation of QCPAxis, especially setRange.
To synchronize ranges, I suggest you connect the rangeChanged signal to the setRange slot between the axes that you wish to synchronize. (You can cross-connect them for bidirectional synchronization.)
Also make sure to replot them synchronously, e.g. by connecting the afterReplot signal to the replot slots of other QCustomPlots.
Generally, if you have multiple plots to show, consider using the layout system of QCustomPlot. It allows you to have multiple axis rects within one single QCustomPlot widget. But of course it's also fine to have multiple QCustomPlots.
Also have a look at the example plot code (click on the images on the start page to see the code). You'll learn alot about QCP just from going through those lines.