Go to your Edit tab for this individual. You will see the list of fields for this individual. From the top find the field birth name (surname at birth). There should be a button to the right saying EDIT. Click this and will take you to another page. It will display the current birth name. Underneath there is a box asking you to what you want to change it to. Type in the surname that it is suppose to be. Clcik the chang ebutton when done.
Once the cheange is made there will be a link to return to this individual's profile. Click this to return to fix the Jr part. Under other last names is a field Suffix. Type in Jr in this field and hit return. Any time hitting return key on the editig page. It will save the data on the profile and relaunch the page. Otherwise scroll down the page to find the button on the left SAVE CHANGES. This will save the data you entered.
NOTE: uploading a GEDCOM sometimes that data in fields get scrambled. For even though this is a universal file. Sometimes software or websites saves their data a little different. When I had done this a few times I got a lot of errors. For the software did not recognize the fields. Best to use one source for keeping data and backup from it.
