About Video codec size

Hello

I have a problem On video Size I will upload a Video On Dailymotion So i will try to Encode
My original Video size 950MB Video Quality AVI (1280x720) 23.98FPS HD720
audio AAS 48000 HZ MP3 But file size 950 MB
when i try to encode This video from Open Shot Video editor file size going to 7.2GB
i have not upload this video online
I have use HD 720p 23.98 Avi format In open shot

Can you please told me how can i create good quality video but small size
If size going to 1-2 Gb that was no problem but orginal was almost 1 Gb but encode 7.2Gb

please help me on it

Thanks