Q: I upgraded to 50G storage in icloud but icloud says i still have just 5G storage. How do I utilize the additional storage I pay for?

If you are asking about when you can use the extra storage, according to this:

iCloud storage upgrades and downgrades - Apple Support

Your plan is upgraded immediately, and the new monthly payment date is updated to reflect the purchase date for the new plan.

If you are asking for various ways to use this extra storage, here are some:

Manage your iCloud storage - Apple Support

iCloud: Upgrade your iCloud storage

Basically they are backup, iCloud Drive, & iCloud Photo Library (Photo Stream).  As a general note, iCloud is a syncing mechanism for you various devices, it is not meant to be used simply as external storage.

Contact link bottom left.

iCloud