брать быка за рога {v. phr.}
brat' byika za roga
~to take the bull by the horns {literally}
Begin to act vigorously, right away and from the most important part. {informal}
Начиная новый курс преподаватель сразу взял быка за за рога. — The lecturer has taken the bull by the horns from the very start of the new course.
To express necessity of doing sth.
Вам наконец-то нужно собраться и начать учиться, взяв быка за рога. — You should concentrate and study, taking the bull by the horns.