I don't use discord, so I'll answer here.
Firstly, are you still here? I'll assume you are.
Secondly, on to business (there might be someone else with the same doubt).
The "standard UI design" people are talking about is: point and click. You have itens represented as icons and spaces to put them, and you have (important) MULTIPLE SCREEN TYPES.
The game screen (with the chars - called dolls - and grass/floors/etc) is the main screen, and along the left edge are shortcut icons to the other screens: map, journal, inventory, character sheet, save/load/options, etc.
To equip the sword, you have to pick it up on the game screen (or buy in a store, but this is more advanced and a topic for an advanced lesson). Point and click on a container where there is a sword/dagger/staff/whatever. The char will move and open the container, and you'll see at the bottom of the game screen a list of itens inside the container on the left-center bottom, and a list of your inventory on the right-center bottom. If you click the sword icon on the left, the icon will transfer to the right (inside your inventory).
Once the item is in your inventory, YOU MUST CHANGE TO ANOTHER SCREEN, THE INVENTORY SCREEN. Click the icon that looks like a backpack, and the screen will change to the inventory screen.
After the inventory screen opens, point and click the sword icon. This click (don't hold or drag, just click) will pick the sword up. Another click in the same spot will put the sword down back where it was. Once you have picked up the sword, move the cursor (that should have changed to a sword pointer after you picked the sword up as above) to the slot besides the char picture and click the slot: the sword will drop in a slot where the character will equip it, and the char picture should reflect that.
Now you should have a sword equipped. To use it: find a character in the game screen with a red circle beneath. This is the sign that the character is an enemy. If you pause (easier to point the mouse in a stactic screen) and move the pointer over the red circle, it will change to a sword. If you click the red circle with a sword pointer, you'll tell your char to attack the red circled character.
That's all for the first lesson on how to use the sword. I hope I made myself clear on this.