How To Connect 3 Phase Transformer in 2 Phase Line

You can't.

Terminology may vary around the world for "line" vs. "phase". For illustration, one might have a 415Δ/240Y transformer with lines/phases ABC and neutral N. For a single-phase 415-volt circuit, you would connect to A and B, B and C, or C and A. (Even though two lines/phases are connected, the waveform is still only single-phase.) For a single-phase 240-volt circuit, you would connect to A and N, B and N, or C and N.

you just scared me

True two phase power distribution with a 90° phase difference is not done any more. What you probably have is more accurately called a split phase where the power lines are 180° different.

To make a split phase power into three phase requires more than just a transformer. A three phase motor driver circuit will work. A split phase motor connected to a three phase generator is also done. It is also the easiest to understand.

The semantics of the term "2-phase".

When i worked at Siemens, it took me a while to figure out this semantics issue, until i sat down with some German counterparts and talked about it.

Outside of North America, they have never heard of true 2-phase power, other than maybe EEs in class. When they use the term "2-phase", they are meaning 2-out-of-3 phases, what we call single phase. For them, "single phase" ALWAYS means phase to neutral.

The only place this gets confusing is in international discussions, like this one. What he meant was that he has a 3 phase transformer but only has 2 lines of his location's 3 phase system to feed to it. He wants to know if there is a way to use that 3 phase transformer as a single phase transformer, and the answer is no.

But as Tornado was pointing out, it may be unnecessary, albeit we do not know what voltage he is trying to attain with the transformer, or if he has a neutral available. Far too little information given to get a meaningful suggestion from afar.

It is not possible..........

Actually the answer is "...it depends..." We really don't have enough information from the OP to give a definitive answer, and as Jraef has said, semantics gets in the way. Nor has the OP provided any info about voltages, ratings, windings, loading, or intended use.

However, if the voltages are consistent with his supply system, its configuration, and the windings of the transformer can be separated in to six separate leads, then it would be possible to use one pair of HV/LV leads to use the transformer as a single phase unit.

There's also nothing inherently "wrong" with wiring across one phase to ground on both sides of a grounded wye transformer attached to a grounded wye system and hanging a single phase load on it; after all a three phase transformer is "just" three single phase transformers sharing a common core.

But if the OP expects to get the full rating or three phase power out of it then "no" is the answer.

You can't do it with a conventional transformer.

The Scott transformer.