Putting case back on automatic.

The back of my automatic Laco popped off (wife dropped it).
I've googled it, and came with only results for quartz type watches but no autos.
Is this something i can do myself or only a watch shop can do?

I've tried pressing it myself to no avail, afraid of breaking both sapphire glass.

I'm not near any watch shops, but will go if it's the only way.