"They have apples."
Translation:У них есть яблоки.
It's optional, but a bit contextual. If you want to say "they have apples", you would certainly say it with "есть" (you will need it in order to stress it). If you want to say "they have apples", you would most likely still say it with "есть". However, if you want to stress "they", you would most likely drop "есть": "у них яблоки", it kind of gets in the way of stressing "they".
What I meant to say is that either a neutral statement, or a statement stressing "have" would certainly use the verb "есть". On the other hand, imagine a situation where your friend just returned from a fruit stall at a local market and you ask him whether they sell pears. You friend responds "у них (есть) яблоки", implying that they don't have pears; apples is all (or the closest thing) they have.
As for the formatting: use the asterisk signs to surround a word. Surrounding it with single asterisks make the word italic, double asterisks - bold, tripple asterisks - bold italic.
Long story short, Russian used to have a complete set of six conjugations for «быть», but almost completely lost it. If you're interested, są is суть, but this form is very rarely seen. You'll only find it used for old-timey effect or in mathematical papers.
The rest four are already history, and I suspect most Russians won't even remember them.