we would usually not say "I have stolen money from my boss" (present perfect tense) we would normally say "I stole money from my boss" (past tense) these are two different verb tenses. the first one is less common, it means you have had the experience of doing something before. whereas the second is simple past tense. http://www.englishclub.com/grammar/verb-tenses.htm

i have told you boss already

Correct ===> I have stolen money from my boss.

안녕하세요, 데이비드님. 영어가 모국어는 아니지만 저도 배우고 있는 처지라 도움이 될까 해서 주제넘게 말씀 좀 드릴게요... I have stolen money from my boss today also = 오늘도 상사 돈을 훔친 적 있다. I stole money from my boss today also = 오늘도 상사 돈을 훔쳤다.

I stole money from my boss. I stole You stole He stole She stole We stole They stole Stole is the past tense of "To steal" and it is correct in the sentence you want to say. Some things in English are better memorized than understood. The same goes for Korean. Don't over-think it.