Mess Up On Installation. What Can I Do Right Now?

I have gotten quite a lot of help to get my hand on Slackware from this community. I get it installed this afternoon/evening. It took four hours or so. The result, however, isn't what I want. There are two problems. First, only Slackware shows up on the boot screen (see the attached screenshot) for an intended dual boot installation. Second, all I have is a terminal for Slackware, where I can sign into a root account I created during the installation and sign out, but nothing else.

Prior to the installation, I made a partition type to Linux (option 83 from the list. Someone mentions "Linux filesystem" on option 20, but I don't see it.) and leave another partition with HPFS/NTFS/exFAT unchanged. Slackware is installed to the partition. Can those two problem be fixed? If yes, how to fix them?
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