You can access the Storage only while in Flarine. A Storage button will appear in the bottom right corner of the screen.

If you are VIP 3 or higher, you will gain access to the Remote Storehouse which lets you access your storage anywhere directly from the VIP Menu.

Note that your storage capacity will increase over time. You will gain a free slot after a certain time, so make sure to check your storage regularly to activate the free slot. Alternatively you can use Diamonds to expand your storage instantly.