Here is the link to the community thread that outlines the methods. The most popular are below. You can also “PM or personal message” the writers in this thread if you still have questions:
Go to Settings from the top bar.
On the side, there is an option to 'Edit Signature' Click that.
Once that box opens up, under the 'font' buttons, there are 'table' buttons.
Click the first one to insert a table, and then you can fill it out.
The other buttons on that row allow you to edit the table (if you need to add more rows/columns) and delete it.
When you get to the settings tab, you will see the edit signature on the left hand side. Click that and 3 lines of options, the bottom row has options for tables. The whole thing is set up in programming language, so you need to click on the options with the A/A - that will take you into WYSIWYG (what you see is what you get). That will mean that you do not have to deal with the programming language. Then you can make a table with columns and rows