i'm not italian and im not that good, except maybe i used to do latin so my grammar was helped by that.
sophie what do u want to know about piacere?
basically it means to please, so when u meet someone or something italians often say piacere, meaning something like "it's a pleasure" in english
when u want to use it to express the liking of something however it becomes more complicated.
usually u will just leave it in the 3rd person form and what u r really saying is this thing is pleasing to me.
i.e Mi piace questa macchina
or maybe it's easier to understand when it's
a me piace questa macchina
u r just saying that "this car is pleasing to me" which is the closest thing italian has to the english "i like this car"
however if there are two cars it would be,
"i like these cars" or "these cars are pleasing to me",
so u have to say Mi piaccono queste macchine
when u change to other tenses u basically leave it in the 3rd person to express like
i.e
mi e' piaciuto il viaggio
gli piacerebbe andare in discoteca con me
etc.
maybe that doesnt clear things up, but i tried
if there's anything more specific u want to know about the verb i can try and answer it/