Using the Wikipedia text editor:

1. Click on "Advanced" at the top of the editing box
2. Click on icon
3. Add data into cells, rows or columns
4. Provide an edit summary and save your work

Another box will appear allowing you to set up the number of rows and columns and style of the table.

Using the Visual Editor:

1. Click on "Insert" near the top of the page
2. Click on "Table"
3. Click on each cell or drag across multiple cells
4. Merge, add or delete cells as needed
5. Click on "Properties" to assign properties to cells, rows, or columns
6. Insert data into cells, rows or columns
7. Provide an edit summary and save your work