I tried to put a placeholder text to edit the "Bio" on the User’s profile, but either it didn’t work or it doesn’t exist. Is there already a placeholder text that allows people to do this? For an example, you can see my public profile on my website: [my website]/My_profile  . It’s where it says, "I was born in the 1840s..." Is there a way to allow people (me) to edit this? 

You can populate your page with a user's info using this Placeholder Text format:

For example, ##memberinfo1memberinfo## for Field 1, ##memberinfo2memberinfo## for Field 2, etc... 

You can find the Placeholder Texts for the other public profile fields in the Public Profile section on your website Admin Panel Social Configurations page -  click on the top "Public Profile" link to jump to that section.  Make sure you have chosen the option "Custom" for the Public Profile Page Type.

Yes, that is the method.  On your website admin panel, Configure Site > Social Networking, Registration section you can add fields to your registration form AND just on your Edit Profile page.  For example, if you want to make the registration process quick/easy with minimum requirements, you can make your added fields, such as the "About Me" field, to appear just on the Edit Profile/Profile page, vs also the Registration page - just checkmark teh box for "Profile Only" on the field.

You did create the field correctly on your admin panel and it is actually working/displaying with the Placeholder Text that you have, "##memberinfo4memberinfo##" on your "My Profile Side Left" page section.  On the test account we created, I added info for this "About Me" field and it is displaying correctly on the test user Public Profile page.

For the "About Me" field, you might want to stylize the field to have several rows - you can do this here also, by just filling in the "Rows" field.

The user’s profile name was not displaying because you had the wrong placeholder text - you omitted the field number in the middle.  I have changed it for you to display the user’s username, by changing the placeholder text to ##memberinfo2memberinfo## .