Provided that "LO" is necessary if you don't specify what you want to learn, you can build up the sentence in two different ways:

LO voglio/vorrei parlare fluentemente
voglio/vorrei parlarLO fluentemente

It depends on what the phrase sounds like in the context of the sentence as a whole.

And in case you haven't studied the conditional yet, "vorrei" is the equivalent of "I'd like", whereas "voglio" simpy means "I want".

Note that, differently from the English language, we don't have to use the personal pronoun everytime: "io vorrei parlarlo" or "vorrei parlarlo" are both acceptable. Getting rid of "io" doesn't make the sentence incorrect. Quite the contrary, it even sounds more natural.

I hope I've been of help!  ;)

GCSE -> fluente

Ho studiato italiano GCSE a scuola e lo vorrei parlare fluentemente.

I studied Italian and I'd like to speak it fluently,is it right? :-)

GCSE -> fluente

Ho studiato italiano GCSE a scuola e io voglio parlare fluentemente

Ho studiato italiano GCSE a scuola, e adesso vorrei imparare a parlare fluentemente.

There are not any real errors, in blue just a suggestion :)