CasaDelGato,
You should select two or more buttons (Shift key+click) to enable the “Same Size” menu item.
Here is the screenshot for your reference.
If you are still seeing issues,
1.Please copy paste the Installation Details from MyEclipse > Installation Summary > Installation Details.
2. Check if the .log which is located at <workspace dir>/.metadata/.log has any errors of interest. If there are any, please paste them here for us.
3. Also attach a screenshot to help us get a visual.
Let us know how it works for you.