Florisa, it goes a bit beyond just "believing". Hearing this on every curse thread is rather annoying. If magic were truly just about belief we would have an awful lot of powerful vampire/unicorn/mermaid/werebeings floating sround site. (and I don't mean the fluffs xD)
Oldor do a bit of magic research. Knowing how magic works is key to successful spell casting. If you know how magic works you wont need to ask others for spells or curses.
I suggest looking up a few different things. Hot foot powder, mars water aka war water, and goofer dust. All three work wonders for curses, and you may learn a bit more about cursing in the process of looking them up :)