The ability to paste a single value and have it fill a range with a single step is not available in ClarisWorks. The easiest way to accomplish this task is to use the following steps:
1. Enter a value into a cell in your spreadsheet document.
2. Highlight the range of cells you want. Single click or drag-select down, then across.
3. Choose Fill Right, and then Fill Down from the Calculate menu (or press Command-R, then Command-D; Ctrl-R and Ctrl-D on Windows).
You could also automate the fill steps above in a Macro/Shortcut if you are using ClarisWorks 2.0 or higher.
This solution also works for ClarisImpact Tables. The only difference is that Fill Right and Fill Down are Available from the Table menu.