All of our modules (or tags) have a div around them, which you can use to specify the size for all of those modules. So you could add something like the following to your CSS file:
.jfbclike {
height: 50px;
width: 200px;
}
This will do it for every like box, which may be good or bad. For even more flexibility, if you're using the actual modules (not the tags), you can use the 'Module Class Suffix" parameter to allow you to set the height/width for an individual (or multiple) instances of a module. Simply use a suffix of "-mylikebutton1", for example, and you can add the following to your CSS file:
.moduletable-mylikebutton1 {
height: 50px;
width: 200px;
}
The module class suffix is a feature of Joomla that most modules use, and are great to take advantage of if you never knew what it was for
Hope that helps, but as always, if you have questions, just let us know!