Learn Turkish: Sekreter dosyaları kopyalasın ve düzenlesin. - Let the secretary copy and organize the files.

This is the 3rd person imperative mood. We take the verb roots kopyala- (copy) and düzenle- (organize) and add the suffix -sın or -sin. This translates to "let him/her [verb]" or "he/she should [verb]". Vowel harmony tells us to use -sın after the 'a' in kopyala- and -sin after the 'e' in düzenle-.

Why do we say dosyaları instead of just dosyalar?

Dosyalar means "files" (plural). We add the accusative case suffix -ı at the end because these are specific files being copied and organized. Whenever a verb's direct object is specific ("the files" rather than just "files"), we must add this suffix.

I see kopya (copy) in kopyalasın. How does the word change into a verb?

You spotted it! Turkish often turns nouns into verbs using the suffix -la or -le. Here, kopya (a copy) becomes kopyala- (to copy), and düzen (order) becomes düzenle- (to organize or put in order). Then we add the imperative ending to that new verb root.