Set table dimensions

Set table dimensions

New user - I created a new sheet, but can't find any way to set the numbers of columns & rows. When I try deleting rows or columns I don't want (select, right click, select "Delete Rows/Columns"), the selected area remains (or is immediately replaced with new cells). How do I make a table with specific rows x columns dimensions? Sorry this is such a basic question. I'm probably missing something simple, but I can't find it in Settings or Properties, & when I search for "table size" or "...dimensions" in the Knowledge Base, it lists articles on cell size, ranges, names, but nothing about the # of rows & columns.