Hi Stephen
If you are using a FlySky i6x that you recently posted questions about, then I would use your throttle channel stick to control both ESC's and use the mixing function on the Tx to feed another output channel on the rx (say5 or 6) and plug your second Esc into that channel. You can control the output rotation by swapping the motor leads if required.
dave976

A good day modelboatbuilder
I usually put 2 motors to one esc and that works fine. But if you have the Futaba with the twin stick I can imagine you would like to use 2 esc so you can turn around the boat at the spot
Regards
Herman lifeboatlover

Your simple fix, if you do not want to have two independent throttles, is to hook both motors to ONE ESC, and ensure your ESC has the capability to handle the amperage draw from both motors
If you choose to use TWO ESCs, and still use one throttle stick, then you would use a "Y' Servo adapter to plug both Controllers into the one Receiver channel slot.

You did not mention the battery or batteries, and how they are connected. This is important!

Most (not all) setups have the battery connected to the speed controller (ESC). The ESC feeds the power to the receiver on the same cable that the receiver also controls the ESC. You will need a "Y" power cable or jump across the motor terminals making a parallel connection.

For two motors the simplest way is with one battery, and one ESC (top part of the drawing). Connect the motors in parallel, + to +, and - to -. Connect the battery to the ESC and plug the ESC cable into the desired channel on the receiver. Make sure the ESC can handle the two motors current (best to use the stall current - amps at a minimum).

If you want to use two ESCs (bottom part of the drawing) you have to be careful. Check the attached drawing - if you use a "Y" signal cable you should cut the red wire in one of the branches so you ae not supplying voltage from both ESCs to the receiver. You will also need a "Y" power cable to supply voltage from the battery to the ESCs like above or use two batteries and wire them direct.

Lew

The easiest way I know of is to use a Y connector and connect both ESC's to it and plug it into the channel of the receiver.

Look at each esc as an aileron you can set up one in aileron channel n one in aux channel then use the various mix features. That way you can set each channel using the reverse Servo switch feature. I’m using Spektrum so I know this works. That way you can have one firward n one revers steering using motors And mix forward backward It might use a helicopter mix to do it all. So elevator stick centered n like a flap or eleven mix put the flap up or down. In this case the Servo or esc will go forward when stick pushed and reversed when pulled. At same time the esc acting like the Servo can make one go right n other left with the stick like an aileron. Just think of the esc as a Servo. So one stick steers n controls speed of motors. While the rudder stick controls the boat rudder. Hope this made sense