If you want the image to be constrained to a particular size, create a 1-cell table with a cell that size, fixing the row height and column width.

Beyond that, if you insert a picture and want to make sure it's a certain size afterwards, right click on it and choose Format Picture > Size where you can adjust the size to exactly what you want.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]