Given your calling it an "Object Repository", I assume you're coming from a QTPro/UFT background?
I was the same.
The Name Mapping in TestComplete is a little different to the Object Repo in QTPro/UFT, but is used in much the same way. What I will say, as you are new to it and this will save you headaches further down the line, is make sure you understand the difference between the full Name Map and the Alias Map.
If your Alias Map is a straight copy of your Name Map, you're doing it wrong. The Alias Map should be a subset of the Name Map. And it should cut out the parts of the application you aren't really interested in (usually series of container panels and frames used to build the page structure). Aliases should also be renamed to be as humanly readable as possible.
So your full Name Map will be a large, technical looking, map of the ENTIRE application. It will have LOTS of layers, be tricky to read unless you do a LOT of renaming, and will be big - as it will contain EVERYTHING. (It has to)
But your Alias Map should be much more readable, smaller, and more like a representation of the application as the user sees it, without all the irrelevant container object they don't care about.
Once you get this worked out and set up properly, it makes using Aliases in you code much more pleasant. It also makes changes to application structure much more manageable. If a few containers change, but the buttons at the end of it do, simply correct the name map and the Alias will continue to work just as it always did. If you find yourself having to update both as a result of container change, in my opinion, your setup is wrong.
You can also use multiple copies of a single Name Map item in the Alias Map, renamed so they "look" different. I commonly do this with container frames which, as far as the user is concerned, are distinct and different panels, but in the background, they actually aren't. But it makes more sense in the Alias Map if they look that way.
And to add to what tristaanogre has already said, yes you can map items using a tool in TC. But, as with QTPro/UFT, expect to have to pay a bit a bit of attention to the properties used and make manual modifications where required if you want things to be reliable long term. It's seldom 100% reliable to use automatic identification properties all the time.