How to work with multiple SIP trunks

Hi everybody,
I have my Asterisk box configured with a SIP provider with one SIP trunk. I use my SIP trunk for outgoing calls only. My questions is as follows:

1 - If I need to use another SIP trunk from the same provider, do I need to configure that SIP trunk in sip.conf as well or it’s not required?
2 - If the answer to the above question is “Yes”, then if how can Asterisk decide which SIP trunk to use for outgoing call?

Please help me in resolving this issue.

Thanks a lot.

SIP trunks are an Asterisk GUI concept, not an Asterisk one.

The dialplan decides which SIP peer to use for outgoing cals.