I bought a relay, but I don't know how to hook it up. it's a 30A relay..
i'm a littlebit confuse the relay have 5 pins but in the diagram it's only says 4 Lead Relay.

 

HERE is the pinout.
Since it's only 12V, you can use a ohmmeter to confirm whats in the diagram.

 

Use your ohmmeter to find the coil, the NO contacts, and the NC contacts.

 

Am i right connecting the wires in the relay and putting the voltage source(12v) in "B" or A (is not inverted)?

 

Its a knockoff of a P&B T90 series with 1 FORM A (SPST) contact. The two pins bonded together internally can be used interchangeably although for 220V you might want to use the one away from the coil to keep the traces / wiring separate.

As drawn, applying 12VDC to the coil (A and B) will close the contact between NO and your red line (?).

 

so "?" in the picture above when the voltage is not yet applied in the coils that part is open?
do i need to leave that hanging when i put the relay in the circuit?

 

Why don't you just use your 12V supply to operate the relay, while you use your ohmmeter to check the continuity on the terminals? You could do that in less time than you have spent typing, and you would learn in the process.