Tempo Trainer Guidance

[forests]

I know this topic has been discussed extensively but I still need a few pointers to get me started. If my post is entirely redundant, please direct me to previous posts that will answer my questions.
Just ordered TT and was wondering where to start? I have been doing TI for 2.5 yrs. now and feel proficient in the basic areas (balance, relaxation, breathing, 2 beat kick, streamlining and overall efficiency). I am 6'0, 165lbs. and stroke count for 25 yds. is consistently 15-16.
However, there is one area I have not mastered and I hope the TT will be able to help me. My practices are all geared to 100 meter intervals because I get too winded to continue without a break. Or is it possible I have been conditioned to this distance? Usually swim 2,000 meters in workout but just in sets of 100's, 3 days/wk.
What kind of TT practice would begin me on this journey of achieving more distance without stopping every 100 meters as I do? Pool is 50 meters.
Thanks in advance for your help/advice.
Steve