A young trumpet vine is easier to arrange than a mature knot of stems. Put the support in place while there is still room to work, then decide which shoots will form the main framework.
Spread selected stems instead of tying the whole plant into one upright bundle. Use soft ties and leave space for stems to thicken. The support must be suitable for a vigorous climber; a decorative twig frame may be adequate at purchase and inadequate later.
Keep access to the plant
Leave a route for inspecting the base, removing dead material and checking the ties. A vine pressed tightly into an inaccessible corner becomes difficult to manage well before it reaches full size.
Check ties during active growth. A loop that was loose in spring can begin to pinch a thickening stem. Redirect a flexible shoot before it hardens rather than forcing it into position later.
Training and pruning are different jobs. Training arranges the growth you keep. Pruning decides what to remove and when. Identify the vine and confirm its pruning requirements before shortening every stem simply to make it fit the frame.
Related reading: Chinese Trumpet Vine Care: Light, Pruning and Training.