Question: I have a question about adding data to attribute tables. I uploaded an Excel file into ArcMap (File -> Add data -> Add XY data). I chose the table from Excel that had the orientation data's latitude, longitude, strike and dip. From there, I made the data permanent by exporting the data into a shapefile. This shapefile was then added as a new layer to my map. From there, using the attribute table in the shapefile, I was able to plot data as points on my map using the latitude and longitude. Then, I changed the symbol from a dot to one representing strike and dip, added rotation to the symbols using the strike, and lastly, labeled the symbols using the dip. This process worked well and I had no problems.

Now, my problem is whenever I edit the attribute table and want to add more data to that table, the new data does not show up on my map and I don't understand why. 

Do I need to add that data to the existing Excel document and then go through the same process?

Answer: 
I suspect that when you symbolized your data, you turned off the "All Other Values" category. If that is true, then new data that is added to the shapefile will not appear unless your new data is attributed with an existing symbol category.

Turning on the "All Other Values" category will cause all un-attributed data to appear with the symbology for that category. Once attributed, the data will appear with the proper symbology.
If you don't want to work on Excel file, you have to edit the point shapefile. Start editing, use the 'Create Features window', click on the point feautre listed, then select 'Point' in the 'Contruction tools' and finally right click on the map area, select 'Absolute X, Y' and add manually your coordinates