I've been doing adWords on and off for years.
For the life of me I can't find where I set times to show and not show.
I am doing exactly what Google Help says :/
It probably looks to me the campaign type settings which you have, which is preventing day parting or ad scheduling options for you. Go to campaign settings>> see which campaign type have you selected. If its standard, change it to all features.
It should help you perform the day parting options which you are looking for.
Welcome to the community
Which is your campaign type? If it is 'standard' please change it to 'All Features'
Find more information about Day Parting in the link below.
Hope this helps,