You have come to the right place. You can attach most (some exceptions apply) sabers together (pommel to pommel) by using a staff coupler. That said, it is generally advisable to have the same two sabers and blade length on both sides (colors don't have to be the same of course) to ensure proper balance when spinning.
With a standard staff coupler, you will have to unscrew the pommels on each saber, and replace them with the center coupler that will attach the two single sabers to form one saberstaff. Alternatively, you can use a quick release coupler, which allows the two sabers to be separated without unscrewing the coupler from each hilt. You just pull down on the coupler sleeve, and it separates the blades from each other without missing a beat, allowing you to smoothly transition form staff to dual sabers, and back.
Here's a video of a US saberstaff with QR coupler in action: