Can't select Startup disk
I have an older Mac (iMac late 2013) and I updated it to Mojave, but it won't let me run my photoshop CS5 (which looking online seems to have been an issue). So decided to go back to an older version. Followed instructions online, holding down Shift + Option/Alt + Command + R when I start the computer, clicking reinstall mac os x, follow the instructions up to selected startup disk and there is nothing to selected. I haven't wiped my hard drive or anything everything is still on it so not sure why it won't come up.
Any help with this would be great.