hi i'm french j'ai un probleme je ne sais pas cofiguré mon nom de domaine mon site c'est smkdgg.5gbfree.com et j'ai achetter un nom de domaine je veut remplacer le nom de mon site par mon nouveau nDD
Well I am not French ;) so can't understand the French Language :), I used google to translate your text I don't know how much I could understand your message but here it is the answer.
If you have got a free host and you want to forward your domain to your free webpage, as you have mentioned like smkdgg.5gbfree.com (I assume that's your website on free host) you can use "Dynadot Stealth Forwarding" feature. You just have to put smkdgg.5gbfree.com and click "Stealth Forward Button" and you are done.
Stealth Forwarding will keep the visitors on your domain while they wouldn't see your domain changing to "smkdgg.5gbfree.com" like normal forwarding does.