不加，直接把tonight放在句前或句末就可以，tonight主要用作为副词、名词，作副词时译为“在今晚，今夜”，作名词时译为“今晚，今夜”。例句：I thought we could go out tonight.我本想我们今晚可以出去。
tonight的相关例句
I'd like to book a table for two for 8 o'clock tonight.
我想订一张今晚8点钟的二人餐桌。
I'd like to take you out to dinner tonight.
今天晚上我想带你出去吃饭。
Now for a summary of tonight's main news stories.
现在是今晚主要新闻综述。
It may freeze tonight, so bring those plants inside.
今夜可能有霜冻，把花草搬进屋来吧。
I think perhaps you've had enough to drink tonight.
我想今晚你已经喝得够多了。