I am making a script mod that is advanced. I want to use XML tuning
to change the game the way I want it. I want to know how to edit the .package
XML for my bidding. If someone can tell me how to do it
I will make the mod and release it.

Do you have velocitygrass' XML editor? See thread (or sticky) in Tools. The download post also has a FAQ with some pointers.

I use: http://modthesims.info/showthread.php?t=537509 and http://modthesims.info/showthread.php?t=534316 I'm confused on how to do tuning

What is your question exactly?

Have you checked out the EA CC documentation?

What are you trying to edit?

What do you want to achieve?

Well I've got a .package file in the program but I don't know what to do from there. I have not done any XMLs before.

Can you please try to explain 1. what you are trying to acheive and 2. step by step what you've done so far? It's hard to tell you anything useful when one doesn't know what package and what program you mean.

The basic idea is that you RTFM (CC guide), then extract the XML from the game (Extractor), then read/search those to see where the ineresting bits are. Then change the files you want, and either import to a package (S4PE) and put that in the game, or dump the file in /unpackedmod. Playtest. Make note of the manifold ways it behaves differently from what you expected, change code accordingly, rinse, repeat.

Were did you get the package file in the sims 4 ??

An XML mod is not necessarily a script mod (and vice versa), though some mods will use both Bear in mind that not everything can be accomplished with XML tuning. XML doesn't create behavior; it just supplies values used by the game's scripts (hence the term "tuning"). If you want to create new behavior rather than modifying existing behavior, you're in script mod territory.

And... nobody is going to be able to tell you EXACTLY how to make the mod you have in mind. If they did that, they would have written the mod, not you You are going to have to figure out most of it for yourself.