How do I replicate a database over 2 geographical sites?
Based on the answers in the comment section, you are looking at a bidirectional transactional replication.

Microsoft document its implementation at this location:
https://support.microsoft.com/en-us/kb/820675

Using the name "Bidirectional Transactional Replication" in your research should help you identify how-tos and step by step tutorials.

Since it's bidirectional replication, you will experience conflicts (a row updated here and there at the same time).

The document explains all of that very well. It's a good start.