Can anyone guide through the complete process of publishing my adalo app?

I’m a complete beginner to the apps world, i am exploring and learning. Can anyone one please guide me to " how to publish my app, what are the credentials? where do i get them? what is an app bundle Id? as i press publish i get to ask for these things.

And can anyone please guide , how much of data can i add for a wallpaper app , as my app has different categories of wallpapers? how much space would I need for more than 500 pics, for an app? and will my app use adalo’s database to access the pics?
Thanks
Waiting for your guidance.

Also i really need to know, how can i attach my GooglePlay account to adalo if i already have one

So your credentials are usually your app’s information, so you would need to purchase a google play/apple developer account and create an app. There should be a step-by-step tutorial on https://help.adalo.com/
Regarding Storage
You would have to purchase a pro account with adalo to receive 5GB of storage and the ability to publish. 5GB can usually house around 500 pictures at 10MB per picture, but you will need to account for users and other information that will use a lot of storage too. If you are new to app designing/making I would start your app on a smaller scale then work your way up especially when dealing with such a heavy backend. Once you get started and start learning the basics of adalo I recommend using XANO as your backend storage so you can eliminate the app slowness/running out of storage and other issues.
If you ever need any help feel free to email me
immannyhernandez@gmail.com