How to say "to give"?
给 is one of these verbs that can also be a preposition (which is quite confusing when you are not used to it). When there is no other verb near to it, it means to give.
Some examples:


给我勇气: give me courage
把钥匙给我: give me the key
叔叔给他一支笔: uncle gave/gives him a pen
杭州给我的印象很好: Literally: Hangzhou gave me a good impression, a better sentence: I was impressed by Hangzhou
我们给敌人一个沉重的打击: We gave the enemy a serious blow


Together with another verb it often becomes a preposition (with implicit meaning of giving something to somebody). Some examples:


我给妻子做早餐: I made breakfast for my wife (= I gave my wife breakfast)
给他看看照片: Let him see the photos
留给他: leave it to him
递给我: pass it to me
送给他: to give him (as a present)
他给我们当翻译: he will be our translator
有事给我打电话: if there is a problem, give me a phone call


There are some other verbs (I already used them in the examples meaning to give). For example


送 (typically used when you give a present)
递 (to hand over)
提供 (to give, to provide + opportunity，surprise，shock，job)


These can be used together with 给in two ways: 送给他礼物 or 给他送礼物, but you can also say 送他礼物.

For your apple example, often depending on the context an extra verb will be added, but you can also say it without. So you can say:


我 给 朋友苹果 (in many contexts this sentence will sound as it is not finished).
我 送给 朋友苹果
我 给 朋友 送 苹果
我 递给 朋友苹果
我 给 朋友 递 苹果
...