Is there a way to share my music and videos from iTunes on all 4 of my devices without paying extra?

No.

Just sync the devices.

Turn on computer. Open itunes. Connect device. Select what you want. Sync.

You should really read the manuals for your devices.

new to all of it. I just wanted to have what i bought to be on all devices

is there manuals on line for all devices. some of the docs are small print