Й is «и краткое» in Russian. It's pronounced: [i kratkaje]. OK, let's explain:
when you pronounce Russian letter «e» after vowel, it consists of two parts: й + э
[о] is in the end of the word, so you should better pronounce but [a] (like in the word luck). You can use [о], but it's dialect, far from Central Russia.
The tip of your tongue will be in the middle of way, after open vowel [а] and before the open vowel [э]. Between two these vowels there will be short й (like the first sound in "yell").
So in russian transcription it will be [и краткайэ] which is [i kratkaje] in English