Select the first cell with the text and then all the cells to the right, as many as you need to cover the whole table width. Then click "merge and center" on the home ribbon.
After that, the table looks like this: Several cells have been merged into one single cell that spans several columns.
Be aware that merged cells should be avoided, because they can be counter-productive when selecting whole rows or columns.
An alternative is to Center Across Selection in the Alignment tab of the Format dialog: Select the cells, then right-click and select "Format Cells". Click the Alignment tab and select "Center across selection" from the "Horizontal" dropdown.
The result will look exactly like the merged cells, but individual cells can still be selected.
The only benefit I see with merged cells is that after Merge & Center, you can format the merged cell to be left- or right-aligned if you don't want the text to sit in the center. With "Center across selection" the text can only be centered.
Another, very simple method is to create borders for the table as you need them, i.e. use just an outside border for the title cell, and all borders for the table body. Then hide the gridlines (on the View ribbon) for screen viewing, or don't bother about that for printing, because gridlines don't print, unless you explicitly tell Excel to print them.