It's a simple process. 

In this file, you will find the functions you need to make your own weapons in a SEPARATE ADDON to be compatible with this addon. 

In YOUR addon file, go to your items and open the file of the item(s) you want to add. In the item(s) file, simply add a tag corresponding
to the category you want the item(s) to be.

A short list:

"tag:myc_def": {}, = can defend and parry with item (for this to work, copy a USE_ITEM_TIME and FOOD component from the mythic weapon items into your item)
"tag:two_handed": {}, = two handed, a slow, but heavy hitting, weapon
"tag:one_handed": {}, = one handed, a simple weapon with decent speed
"tag:myc_kat": {}, = a katana, very combo-heavy weapon, may take a bit of more time to edit than most weapons

---

Now, in this folder, you will COPY AND PASTE THE "functions" FOLDER into YOUR addon. 
Inside of it, you will find the tick.json file and the function file necessary to make your weapons work. Do NOT keep "(youraddonname)"
in the tick.json file OR on the name of the function file. Name "(youraddonname)" to anything UNIQUE to you. This is to be sure you do not
interrupt any other addons with the same files.

Now, in tick.json, you do not have to do anything BUT change "(youraddonname)" to the name you selected for the function file.

In the function file, depending on what weapons you have added, you will change the damage of the weapon and its range/AOE in the file.

Don't stress, it's not hard.

Each different section plays a sound and uses a damage command.
Each row in the section is a different part of the combo in-game.

Do not change the score values, but do change the HASITEM part to the SAME identifier as the item you wanna add.
Now, all you have to is change the AOE and damage.

AOE is simple. In everything about "damage" part of the command in one row, you will see something like "r=5" and "^ ^1 ^5".
Basically, it has a 5 block AOE in front of the player. Do not EVER let the "r", or radius, outweigh the reach, or the third "^" in the command.
As you'd guess, "r=5" and "^5" correspond to each other. Change these depending on the AOE you want.

Finally, the damage. I don't think I have to explain, but just edit the damage in the row. "damage @e[r=5] >5<", the part I highlighted is the damage.

Have fun.



(EXTRA)
Hey, if you know a thing or two about scoreboards, you probably know how this addon works.
If you are crazy enough, you can create your own particles and animations, then use the scoreboard timer to add you particles and animations without 
interfering with other addons. Granted, you'd still be given a time limit set by the engine, but you could make some cool stuff if you tried.