Welcome! 
First, let’s back up.
The IDE was part of the old pre-2023 architecture and is no longer available. Things are managed now in quite a different way. So any blog posts or videos or forum post you find that are dated before August 2023 are probably out of date and will just be confusing.
Why don’t you start by reading the community FAQ on the new architecture and it should give you the basics you need to know to follow everything else.
FAQ: I have no idea what Edge is. Is that a new developer tool? (2022)
Once you’ve read that, it’s important to understand that not all Zigbee devices will work with smartthings. The independent third-party Zigbee standard allows for “manufacturer proprietary” clusters, which can be unique to one manufacturer. For example, one of the largest home automation companies, tuya, uses a lot of proprietary code in its devices. So it can be sometimes tricky to get those to work with smartthings. But may be doable. Also, there is more than one Zigbee “profile“ and not all of those work with smartthings.
The first rule of home automation always applies: “the model number matters.“ So we will need to know the following:
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what country are you in? (The device and feature selection does vary)
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do you have a smartthings/Aeotec hub, and if so, which one?
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what is the specific brand and model for the device that you want to add to smartthings? We can start with just one, that would probably be simpler.
Anyway, welcome again. I know it probably seems a bit overwhelming at the moment, but there are lots of people here who will be happy to help you figure things out. start by reading the community FAQ because it will give you the basic ideas and terminology you will need