Learn Russian: Врач работает утром, а также вечером. - The doctor works in the morning and also in the evening.

In Russian, to say when an action happens during a part of the day, you change the noun's ending. The dictionary words утро (morning) and вечер (evening) take the -ом ending (this is called the Instrumental case) to become adverbs meaning "in the morning" and "in the evening".

Where is the word for "in" before утром and вечером?

You don't need one! While English uses the preposition "in," Russian just changes the ends of the words. The special ending on утром and вечером does all the work for you.

What exactly does а также mean, and why is there an а instead of an и?

А также is a fixed phrase that translates to "and also" or "as well as." Even though и is the most common word for "and," а также is the natural Russian way to add an extra piece of information to a statement like this.

If the doctor happens to be a woman, does the word врач change?

No, the word врач stays exactly the same. Even though it is a grammatically masculine noun, it is the standard professional title used for both male and female doctors in Russian.