How do I use 'weil' (because) as a conjunction.

'Weil' is a subordinating conjunction. This means that it can be used to connect a main clause with a subordinating clause.
For example, Ich liebe Schokolade, weil es lecker ist. (I love chocolate because it is delicious) 'Ich liebe Schokolade' is a main clause - it makes sense when used on its own.'weil es lecker ist' is a subordinating conjunction because when it's used on its own, it doesn't make sense.
To use the subordinating conjunction, 'weil', you have to remember that it is a verb kicker. This means that it changes the order in which a verb is placed in a sentence. Normally, the verb always comes second, but when 'weil' is used, the verb gets kicked to the end of the sentence.
For example,Schokolate ist lecker.Ich liebe Schokolade, weil es lecker ist.
Once you get used to kicking your verbs when you use 'weil', you can easily use other subordinating conjunctions like 'da', 'obwohl' and 'dass'.