[KubiK888]

Currently the items in the top menu bar is left-aligned, how can I change it into right-aligned?

[Robkk]

Link to exactly what you are talking about. What menu items?? I think this is also something in your theme, unless your are talking about the profile menu items on the users profile.

[KubiK888]

Hi this is the link, Epilens.com, I am talking about the top menu (with login and register items).

[Robkk]

Not really a bbPress related question, but use this.

ul#menu-secondary-menu {
    float: right;
}

Make sure to keep it bbPress related next time.