A delay gate provides no logical function. Its only purpose is to delay the change of a signal between its input and output.
Set the (propagation) delay of the delay gate by typing or using the keypad.
By default a single delay gate is created, with each input being a single wire. Multiple delay gates, with the input being a bundle of wires, can also be specified by typing or using the keypad to enter the desired number of gates in the "Gates (bits)" field. The resulting single gate symbol will then be a shorthand for multiple delay gates, with the input of each gate being the corresponding bit position from each wire in the input bundle. For example, specifying two gates (bits) will produce the equivalent of two gates (one symbol), with the input of one of the gates being from bit position 0 of the input wire bundle and the input of the other gate being from bit position 1 of the input wire bundle.
A delay gate can point in any of four directions: up, down, left or right. Pointing right (the default) means that the output of the gate is to the right of the inputs. Select the orientation of the gate you are creating by clicking on the appropriately labelled button.
To finish the dialog and place the newly created gate, click on the OK button. Then move the mouse to position the gate where you want it in the circuit and left click to fix it in that position (it can be moved later, so don't have to be in exactly the right spot).
If you change your mind and decide you don't want a gate of the type you are currently creating, click on the Cancel button in the dialog. If you have already clicked on the OK button but have not yet fixed the place of the new gate, you can still cancel the gate by right clicking the mouse.