To begin with, you should follow this path:

<drive with the installed game>\SteamLibrary\steamapps\workshop\content\322330\2049905964

The folder that opens will contain a file "modmain.lua" that needs to be opened using any text editor (even the default Notepad will do). In the opened file you need to press Ctrl+F which will open the search menu. You are interested in the following arrays:

• local weapons — An array with all melee weapons
  
• local rweapons — An array with all ranged weapons
  
• local axes — An array with all the items that can cut down trees
  
• local pickaxes — An array with all the items that can mine rocks
  
• local shovels — An array with all the... shovels? There aren't that many of them
  
• local dtools — An array with all tools that are capable of dismantling buildings
  
• local gtools — An array with all garden tools
  
• local scythes — An array with all scythes. Not active by default, scythes are added by the corresponding mod
  
• local canes — An array with all hand items that speed up movement
  
• local armors — An array with all body armor
  
• local helmets — An array with all head protection equipment
  
• local lights — An array with all possible light sources

In any of these arrays you can add the items you need, following simple rules:

1. All item IDs must be in quotes ("")
   
2. There must be a comma after each ID, except the last one
   
3. The closer the item is to the beginning of the array (closer to line 1/higher line), the higher the priority of the item

In most cases, item ID can be found on wiki under "spawn code".
You can also remove unnecessary items from arrays, following the same formatting rules.

Don't forget that after updating the mod version all your changes will be overwritten. I advise you to make a backup!