Where can I go through the customs formalities?

我该在哪儿办理海关手续?

Over there, just around that corner.

就在拐角处那边。

You're through with the Customs formalitie.

你已办完海关手续了。

Give this form to the customs officer standing at the exit.

把这张表交给站在出口处的海关官员。