"We are reading."
No, the personal pronoun (εγώ, εσύ etc) is optional in Greek. This is explained in the Tips & notes for this skill. You can find it at the top left of each exercise page.
How do I place the accent directly OVER the "i"? When I type Shift ;, the accent appears above and to the right.
On my keyboard, i press this (;) button (next to L) and then the letter.
Is it really true that this whole sentence can rightly be written with the single word διαβάζουμε?
Yes, because we, εμείς, is implied by the ending of the verb. Εμείς is used when we want to emphasise that we are doing something as opposed to someone else.