What to say: 如何预约
I need an appointment.
我需要一次预约。
I'd like to schedule an appointment.
我想要安排一次预约。
Would Wednesday at 3 pm work?
周三下午三点可以吗？
Does he or she have any time on Wednesday afternoon?
他/她周三下午有时间吗？
I need an appointment on 24th. Is there anything available at that time?
我想在24号安排一次预约，那个时间有可以预约的吗？

How to agree that a time works: 如何给出肯定的回答
Yes, that's perfect.
可以，那太好了。
That should work.
那应该可以。

How to say you're not sure if a time works: 如果不确定时间可以怎么说
Oh, that may work. Let me check my schedule and call you back.
那个时间应该可以，让我看看我的日程表再给你回电话。
That's a possibility. Can we book that for now and then I'll call to change it if I need to?
应该可以，可不可以我先预约这个时间，如果有变动我再给你打电话？