To add these items to your NWN2 character you can use the in-game console, the Silverwand Item Summoner, or purchase from the Silverwand Magical Emporium.

To add an item with the console giveitem command or the Silverwand Item Summoner you will need to know the item's tag, which is the part of the file name preceding ".UTI". After subscribing navigate to the appropriate sub folder in C:\Program Files (x86)\Steam\steamapps\workshop\content\2738630
If you look at the contents you can see which files are UTI files. If there is documentation you should read it,

Using the console giveitem command will disable achievements, so to reenable achievements save the game and then edit the file globals.xml in the saved game folder, changing the 1 to 0 (zero) in these lines (credit to Aldroen):
<Booleans>
<Boolean>
<Name>ShowCheatsWarning</Name>
<Value>1</Value>
</Boolean>
<Boolean>
<Name>Cheater</Name>
<Value>1</Value>
</Boolean>
</Booleans>

When you subscribe to a mod and it is downloaded Steam will create a subfolder in C:\Program Files (x86)\Steam\steamapps\workshop\content\2738630 for its contents. You can look in that subfolder for the files. Items are UTI files.

How do you get these weapons in the game? Do you have to craft them, or do you get them by killing enemies?

Thank you

The shadowblade tag is bb_shadowblade

Can you tell me the id of Shadowblade?