Worldedit CUI is optional on the server, and is useful to have if you want to select areas using the worldedit wand.
To install Worldedit CUI on FTB Unleashed, you first need to download Liteloader, and the Liteloader version of Worldedit CUI for 1.5.2, which can be found here.
Next you need to run the FTB Launcher, select Unleashed, and click the "Edit modpack" button. On the window that comes up, select the mods tab, and add the Litemod file to it from your downloads folder by using the "Add Mod" button, Next, select the Jarmods tab, and add the Liteloader zip file from your downloads folder by using the "Add Mod" button.
When you next run the pack, you should have WECUI installed. To check if it was installed correctly, craft a wooden axe, and select 2 blocks. If a graphical mesh appears, it has been installed correctly.
"I can't select blocks with the wooden axe"
To enable block selection, do /toggleeditwand, and vice versa.