If you put "onlar" at the beginning then its optional to put lar/ler to the verb, and if you put lar/ler to the verb then its optional to mention "onlar" at the beginning. In other words if you put the doer name at the beggining (sen, ben, siz, onlar, o, biz) makes it optional to put the verb additions (-rim, -sin, -siz, -ler,... etc), and vice versa.
There is no plural in sentences without the case accusative. You use as singular:
I read newspapers / books / magazines - Ben gazete / kitap / dergi okurum (plural, implies that is plural because there isn't "bir")
I drink beers - Ben bira içerim etc.
But, if you write a sentence in singular , use "bir" (a/an - indefinite article)
Here is using "simple present tense" in Turkish:
You don't need to use the word in parentheses. Also, "gazete" means a newspaper or more than the one.
(Ben) gazete okurum - I read newspapers (Sen) gazete okursun - You read newspapers (O) gazete okur - He/She/It reads newspapers (Biz) gazete okuruz - We read newspapers (Siz) gazete okursunuz - You read newspapers (Onlar) gazete okurlar "or" Onlar gazete okur - They read newspapers
I read a newspaper - Ben bir gazete okurum (singular)
I read newspapers - Ben gazete okurum (plural)
I read the newspaper - Ben gazeteyi okurum (singular)
I read the newspapers - Ben gazeteleri okurum (plural)
Notice this difference good. ;)
If you use "bir" (indefinite article) in a sentence, then is understood that is singular, and without "bir" is plural in Turkish.