Which wallet are you using?
If you are using bitcoin core, you can click "Add Recipient" at the bottom of the send tab.
If you are using blockchain.info, you can click "Custom" on the left and the + sign on the right of the send money tab.
But how can you pay at the same time? like, i want to send 10 people X amount, there should be a way to post all the addresses you want to send to, the amount, then click "send" and you are set, all the transactions happen at once. I dont know if you follow me.
Say, if you want to create one single transaction to send bitcoin to 10 different addresses, you just need to click "Add Recipent" 9 times in bitcoin core and enter all the 10 addresses and payment amounts.
Then you just need to click "send" and it will be done.
For blockchain.info, you just need to click the + sign 9 times. I am sure other wallets allow you to do the same as well.