Hi! In my opinion, none is wrong. However, which one could be appropriately used depends on the situation one is in. For example:
"I have graduated in Computer Engineering" uses present perfect tense which represents the action of graduating in computer engineering having completed and therefore may be used in situations where one would intend to refer to one's current endeavor having completed and further speak of one's future plan(s), for example :
I have graduated in computer engineering. Now I am deciding on what to do further.
However, if used alone, the sentence may indicate as to what milestone in education one has covered.
'I have got a degree in Computer Engineering' particularly indicates ones academic qualification. That is, it tells that one holds or possesses the said degree.
"I graduated in Computer Engineering' uses the past indefinite and therefore refers to an action completed somewhere in the past. In this sense, it could be used while talking about a series of past events one of which would have been graduating itself. However, in American English, according to my knowledge, past indefinite or simple is also used by native speakers as an alternative to present perfect, in order to refer to an action that completed in the very recent past as in :
"Yay! I passed my driving test" an alternative to the British "Hurrah! I have passed my driving test" or
"Where did the car go"? which means the same as the British sentence: "Where has the car gone"?