This is the 1787th most frequent Russian word.
используйте
"Use" (imperative form).
In this sentence, 'используйте' is an imperative form of the verb used to instruct someone to make use of the book for a specific purpose.
Используйте эту книгу для изучения русского языка.
Use this book for studying the Russian language.
Here, the verb refers to the action of utilizing an application for a functional objective in a general indicative context.
Вы можете использовать эту программу для обработки данных.
You can use this program for data processing.
In this case, 'используйте' is again an imperative suggesting the adoption of a fitting method to achieve a goal.