"After the party I am going to bed."
Translation:Po imprezie idę do łóżka.
I don't know who put this hint there, it definitely comes from another sentence, possibly from the English for Polish speakers course. But I guess it sounds reasonable, added.
"kłaść się" = "to lie down", in a proper context we can assume that it's lying down with the intention to fall asleep. So "kładę się spać" and "kładę się do łóżka" make sense to me, but so does "kładę się" on its own.
I am looking for simple ways to understand all these cases ... the chart containing the affixes lacks an explanation of when to use the cases... as a summary. I.e after a preposition use the locative case ... sorry if I sound like dummy but it certainly is complex to deal with the declension system already.
Certain prepositions require certain cases, sometimes different ones, depending on which meaning you want to convey.
In this sentence, it's the genitive case, which is required by the preposition do. For other uses of the genitive, check out this link: