It's time for some business idioms. You may use the following idioms even in ordinary situations.

Business English Idioms You May Use for your Presentation

Meaning:  Getting the permission from someone in authority. Sometimes, we also say the ‘Go Ahead’

Example: As you can see, the systems are all in place, so all we need is the green light from you to get started.

Meaning: Easily available

Example: You should always have the latest sales figures at your finger tips in case you are asked about them.

Meaning: Let things happen.

Example: You might get some technical interruptions but don't worry, just go with the flow.

Meaning:  to have a few secret plans

Example: I like to have a few extra tricks up my sleeve in case they  are needed.

Meaning: forgetting something. 

Example: My biggest fear about giving a presentation to a large audience is my mind going blank.