What are the steps to take to fill out a travel voucher on DTS?

Without looking at DTS as I type this, you would log into DTS and in the upper right area of the page after Log In, there should be a box to click with options. You will select "Create Voucher" (not local voucher). Then, you go thru the steps. It's a hell of a lot easier nowadays. You will eventually get to a spot where you have to upload your airline itinerary as substantiating documents. Eventually, you will digitally sign it and submit for review/approval. If it all went well, then it'll be approved. If there are any errors, your DTS Approving Authority will return it with instructions on what is missing (if anything) and what corrections need to be made.

If in doubt, is there anyone at your unit (Training NCO, Platoon Sergeant, etc.) that you can call to get assistance in a Step By Step over the phone instructions?

This might help you. https://www.google.com/search?q=dts+smart+book&sxsrf=ALeKk03Ly7-vkeQJIahfPBJ4rawHMBPY-w: [login to see] 42&tbm=isch&source=iu&ictx=1&fir=mfRYtBZ1RjmQDM%252CGd-QXZ-E62T8YM%252C_&vet=1&usg=AI4_-kQw8iAmwY4w3-Oe7MPAzZJ8Va8KDg&sa=X&ved=2ahUKEwiMl8Wwy5vsAhVB5awKHR2BCfQQ9QF6BAgKEEc#imgrc=mfRYtBZ1RjmQDM