Question Why won't my computer display my screen or power up keyboard and mouse

[Fml123]

I just finished making my new desktop and it dosent display the screen.the mouse and keyboard are not lighting up. it is my first build but everything in the desktop turn on all my fan starts. All the pieces are new.

MSI Geforce GTX 1050 TI
Patriot viper steel kit ddr4 8G (2x)
ASrock atx b450 pro4
AMD ryzen 3 3300x
MSI MPG A850

 

[Fml123]

Nvm i'm stupid dont forget to plug your ram a1 to b1 lol