The difference isn't in the memory, it's in the CPU/Motherboard.
"Dual-channel" memory means a motherboard which optimizes memory access for PAIRS of DIMM modules.
"Tri-channel" memory means a motherboard which optimizes memory for groups of 3 DIMM modules.
If you bought "Tri-channel memory" for a dual-channel motherboard, what it means is that you bought a kit of 3 DIMMs. If you want to get optimum performance in your dual-channel motherboard, just plug in 2 of the DIMMs and leave the 3rd one on the shelf.
If your motherboard has six or eight sockets, you could get a second 3-channel kit with 3 more DIMMS and plug in all six of them - that way you'd have three PAIRS running at optimum speed.
If your motherboard has four sockets, you could by ONE more DIMM module with the same specifications as the other 3 and plug all four of them in for optimized memory speed.