If you include the date and time information in task name when creating a new Task, TickTick will automatically recognize the date as the due date and set a reminder based on the time.
For example, if you want to go to gym tonight at 8 pm, just type "Go to gym at 8 pm", the new task "Go to gym" will be created and there will be a reminder at 8 pm.
You can choose to keep the date information in the task name or remove it. For the latter, just go to Settings > Task Quick Add > Smart Recognition > Select Remove Text in Tasks.
Here're some examples of the date formats you can use in TickTick.