Help With 50% Pre-Payment To Supplier

Hello Experts

I am a new user of SAP B1

We have some supplier who require us to make a 50% pre-payment before the goods are dispatched to us

Can someone please help me in how do i go around doing this

I have read about using the AP Reserve Invoice

But i have never used this option before

If someone could explain it to me step by step in the process of doing it

I would very much appreciate it

Thank you in advance