My iCloud is almost full but it shows two phones in it.

Go to Settings>General>Reset, tap Erase All Conent and Settings and enter your password when prompted. This will not effect your new phone. (Back up to iTunes before erasing it if ever want to access any of the content on it again in the future.)

Yes, do it on your old phone, but make sure you have all the data on your new phone before erasing it. If you don't, restore the backup of your old phone to your new one before erasing the old phone to make sure the data successfully transfers to the new phone.

Then you can safely erase the old phone. Also, if you have an iCloud backup of the old phone that you no longer need, you can delete it from your iCloud account to free up the storage that it occupies. To do this, go to Settings>iCloud>Storage & Backup>Manage Storage on your new phone, tap the name of your old phone under Backups, then tap Delete Backup. If you go to icloud.com from your computer, open Find My iPhone and still see the old phone listed as "offline", you can hover your mouse over it on the Devices list, then click the "x" to remove it from the list.

Yes, erasing the old phone won't do anything to the new phone, nor will deleting the old iCloud backup or removing it from the Find My iPhone devices list. But if you're concerned, you can back up the new phone to your computer first by connecting it to your computer, opening iTunes, then going to File>Devices>Back Up. Then go to File>Devices>Transfer Purchases. After doing that, even if something went wrong, you could restore this backup and no lose anything on your new phone.

this helped me a lot thank you