から can have several different meanings in Japanese, depending on which part of the sentence it is in, and what comes before/after it. It is often translated as ‘because’, or ‘since’. In these cases, it just means ‘Because of (A), (B)’.

• 昨日（きのう）、アイスクリームを沢山（たくさん）食（た）べたから、お腹（なか）が痛（いた）いです。
  Since I ate so much ice cream yesterday, my stomach hurts. (From that I ate so much ice cream)
• 彼女（かのじょ）は優（やさ）しいから、好（す）きです。
  Because she is nice, I like her. (From that she is nice)

から may be used with almost any type of word, but when the nuance is ‘because’, it will require だ before it after a noun or な-Adjective.

• 大（おお）きい会社（かいしゃ）だから、人（ひと）が沢山（たくさん）いる。
  Because it is a big company, there are a lot of workers. (From that it is a big company)
• スマホは便利（べんり）だから、人気（にんき）がある。
  Since smartphones are useful, they are popular. (From that they are useful)

Despite having several different nuances, it may be easier to think of から as meaning ‘from’ in all situations, as that is the base nuance.
From (A as a reason), (B) = Because/Since
From (A as a location), (B) = From