I've got quite a bit of old DOS software (And paper books/manuals) some of it is commercial (WordPerfect 5.1, PCPlus, etc) and other is shareware.
On a more practical note, if you have factory-pressed original disks and manuals, those are fairly easy to sell. I'll assume you are talking about eBay, but this could apply elsewhere.
Separate out anything that has both the original disks and manuals for individual sale. Make sure all disks of a set are present. Boxes are a plus, good condition is a plus. It is nice if you can verify that the disks are readable.
Any other original disks with titles that stand out, you may wish to sell individually or as a small lot. A small lot is more likely to move faster.
The rest, you would probably need to sell as a lot of "assorted MS-DOS software". List the titles, and provide readable photographs of the disks showing their labels. List titles as clearly as possible in the description. You may explain if it includes registered shareware here.
Old personal collections of floppy disks show up periodically. However, in general, buyers don't seem to care for non-factory original disks.
Registered shareware is problematic as it is often registered in one person's name. On the off chance there is still support for it, the vendor might choose to not transfer support to the buyer. I've also seen some programs that encode sort of a hash of the user name/company in the provided serial number, so both must match when they entered them. Others write you name in to the executable. Not very desirable.
In other words, you will be lucky to get the price of just a used floppy disk.