Learn Spanish (Spain): Escríbelo aquí.

To give an affirmative command to one person (tú), you use the same form as the he/she/it present tense. Since the verb is escribir (to write), the he/she form is escribe.

Why is the word lo attached to the end of the verb instead of coming before it?

When you give an affirmative command (telling someone to do something), you must attach object pronouns like lo (it) directly to the end of the verb. You cannot say lo escribe when giving a command; it has to be combined into one word: escríbelo.

Why does Escríbelo have a written accent mark?

Attaching lo to the end adds an extra syllable. To keep the spoken stress on the exact same letter as the original verb (escribe is naturally stressed on the i), you must add a written accent mark to show where the emphasis belongs.

How would I change this sentence to say "Write it here" to a group of people (vosotros)?

To form the vosotros command for escribir, you replace the final -r with a -d, making it escribid. Then, you attach the pronoun lo to the end, which makes it escribidlo aquí. Notice that escribidlo doesn't need a written accent mark because the spoken stress falls on the correct syllable naturally.