Just to add to what AiTenshi1 has already said...
The easiest way to create a rule for an existing mod is to...
- Select the plugin in the Masterlist panel as suggested by AiTenshi1
- Right-click and select Create Override (or click Create Override on the Toolbar)
- Select the location in the Masterlist that you want your new rule to be placed (a plugin or Group)
- Double-click to move it to the Sort Object (you can also right-click and select from the menu or click Sort Object on the Toolbar)
- Use the drop-down Menu to describe whether it goes after or before the plugin (or at the top or bottom of a group) - BUM will suggest a default
- Click Save Rule (or move the cursor over the Rule list)
- You are done
Main difference from what AiTenshi1 described is that you do not need to use Copy Name to create a rule - Create Override and Create For do this automtically.
Use Override to change to a mod's placement.
Use For to add or change Bash tags.
Hope this helps.
Edit:
Added a step that I forgot to include
lol I actually did it pretty similar to how you described it.
Yep, that works, too.

I think the main thing about help files is that most people don't read them (like game manuals, right?) In the case of a help file that seems long/complicated for the average user, that's even more true (i.e., even if they look at it, if it seems like work, they'll skip it and try to simply use the program, then blame the program if it isn't user-friendly enough). Your helpfile in BUM is written in a way that is easy for almost anyone to understand while the BOSS helpfile is definitely more detailed, lengthy, and complex. I skimmed the BOSS help, of course, but then decided to use BUM, so it didn't even occur to me that I would need to read the BOSS help more thoroughly.

Since BOSS is basically a subroutine for BUM, I would expect BUM to include any specific help necessary, or point to the BOSS information if needed. I think people who have used BOSS extensively for awhile might have a different perception, but I didn't use BOSS until a few months ago with FONV (most mods I used were not recognized and there were errors in LO for some that were, so I didn't find BOSS very useful back when I first tried it). For new Skyrim players, I think that their perception is likely to be closer to mine, at least if they use BUM as their primary tool for LO management.
Just offering a different perception.

I did actually look through the help section several times but couldnt find where it said how to do such a action.
Based on the advice I have seen you providing, it has made me think that it would be a good idea to include a mini-tutorial in the Help that explains the basics.
I have always viewed BUM as a BOSS add-on and so made the assumption that people would start with BOSS

Many thanks for your insightful feedback
That would probably be pretty helpful. You might want to look at it like this. As popular as skyrim is and as booming as the modding community is, your going to be getting a lot of new people who will be referenced to BOSS and BUM. A quick basic tutorial for the common things that they will need to know will be very helpful.
Look at me, i've been dealing with mods since Oblivion and didnt see a reason to get BUM because A) i didnt know half as much as i do now, and

because the utilities worked so well. Skyrim on the other hand has changed many things and has made it almost necessary to have both BOSS and BUM to make the files load correctly. Now I have to learn about a completely new program and while the help is useful I couldnt find information i needed for a specific task.
So yeah i would fully support the idea of a turorial of sorts for the basic need to knows and how to's.