I do not understand what it is you are referring to here. You can't change the amount of storage space a device has. I am going to guess that you really mean you want to remove things from the device to free up storage space?
If that is the case, then there is only so much you can do. The OS and many preinstalled apps will be taking up a lot of that space. You can uninstall some apps. Either ones you installed yourself, or ones that were preinstalled, are not necessary, and will let you uninstall them. With apps that you can't remove, but are updated, you can remove the updates for them to free up some space. But all that is limited.
If you want to just move files (photos, videos, music, etc.), not apps, to the SD card you can use the...