If you click on Help/About, this will tell you whether your version is 16-bit or 24-bit. If it’s 24-bit it will say “n-Track Studio 24 bit” as the first line of text. If not you would have to upgrade to the 24-bit version of n-track to be able to use your Delta 44 in 24-bit.
If you have the 24-bit version, to set the soundcard to use it, go to the “Recording Vu meter”, then click on the hammer icon. You will see ther various options there. Select 24-bit and Standard. You can actually set this up in the 16-bit version as a test, but I believe n-track inserts a noise every few seconds.