Wait. I know you really want to get it done and running. Understood. Wait anyway.
But while you wait look (aka "google") for, then read and watch various tutorials on building your own PC.
Watch and keep notes about things you do not understand in any manner. Then do additional searching accordingly.
Start here (no insult intended) just a great starting point:
https://www.tomshardware.com/news/build-a-pc-for-kids,35304.html
https://thenextweb.com/gadgets/2017/07/30/build-desktop-pc-reference-guide/
https://www.howtogeek.com/howto/the-geek-blog/building-a-new-computer-part-1-choosing-hardware/
Find more such links as you deem necessary. There may be assembly differences but you should be able to understand the what and why between the differences in how the build is assembled.
After doing the above do a "paper build". Write down the steps and actions that you believe or otherwise understand to be necessary for your specific build. Part by part. Create the plan in detail and be specific. Use a separate page for each step.
Last of all. When you do start building take your time. Work in a clean, well lit area. Have your tools ready. Check the tools. You want screwdrivers for example that properly fit the screwhead. Not too big, not too small. Otherwise you may damage or even break the screw to where it cannot be used or removed.
A magnifying glass and small bright flashlight may be very handy.
Do not force things. Initial fits can be tight but the connections should be a matter of finesse and not force.
Stop if you get tired, something does not feel right, or there is an obvious problem. Take breaks, keep notes about what you did and again do additional research when something is not as expected.
Copy or photograph any component labels for future reference. Record all components: make, model, version, and serial numbers. Especially if the label/plate is "buried" inside.
Treat everything carefully, keep the work area clean, store extra parts, adapters, packaging the original box or bag. May be needed if some component must be returned. Keep all purchase and shipping information for the same reasons.
Last but not least. Read the instructions. All of the instructions. Several times.
Verify that the instructions do match the component you received. Do not overlook addendum documents with corrections, verifications, and possibly warning information. I.e., the "DO NOT...." stuff.
Unpack carefully, ensure that you do not leave some scrap of packing material somewhere that will get in the way and jam things up. Or lose some tiny plastic bag with vital screws, etc...
Check the installation diagrams. Verify that all parts are present. Measure distances between components and fasteners. Examine screws and fasteners to ensure that they are not bent or damaged. Very bad if some screw is forced into place and then snaps off....
And I will hope that other Forum members will add other suggestions. Lots of "lessons learned" out there.....