I can make a small tutorial here. (If you never worked with creation kit, this should even be do-able) I don't know if you are (very) experienced with making mods, so I'll make it so everyone can follow. (also for others)
These steps are very basic, for people who never worked with the Creation Kit (CK)
First install creation kit. It should come with Skyrim and can be found in the Steam Library under 'Tools'.
1. Open creation kit.
2. Click 'File', then 'Data...' and tick the 'Skyrim.esm' box. Then click 'Ok'.
3. Say 'Yes to all' on all popups. If it crashes, search the internet (or ask here). Some errors occur a lot.
Now to editing the subtitles:
1. You won't need the render window or the cell view, so you can make the object window fill the whole screen.
2. Click on the + before Character (in the object window) and then click on 'Quest' (just the word. The + shows different categorys of quests)
The quest tab holds a lot of information. Quests are obviously in it, but also dialogue is. (most) quests with a name (see the 'Name' column) are actual quests.
3. Now you can use the filter (upper left of the object window) to search for specific things. The filter will look through the Editor ID's (first column). Generic dialogue often holds information which NPC's say when you are for example trespassing in their house. A few more things to search for:
CW = civil war
MQ = main questline
DB = dark brotherhood
TG = thievesguils
name of a city shows dialogue in that city
Follower = dialogue from followers
There are loads more, but this is a start.
Once you found a quest or dialogue that you want to translate:
1. Double-click the name or the yellow icon.
A window pops up.
Depending on the type of dialogue you opened, you may find the tekst in different places. I will discuss both using the DialogueGeneric editor ID.
2. First open the tab 'Dialogue View'. It has one editor ID, namely 'DialogueGenericView'. Click on that.
3. You now see some things in the white space. You may have to move the blocks of text. You can do that by clicking on the orange bar and dragging the box around.
If the box 'show all text' is ticked, it will (obviously) show all of the text. Some things will have text in the orange bar. This is something the player says. (I would not change that to Dovahzul ;) )
4. Double-click the orange bar which says 'OfferServicesTopic: What have you got for sale?'.
You will have a new window again.
Now you see all of the possible replies, depending on the NPC.
5. Double click 'So you're interested in my potions and ingredients?'
6. Double click this sentence again in the new window (in the 'Response Text' box)
7. The text should be selected in the (again) new window. You can now translate it and retype the text.
8. Once you're done, click 'Ok' on all windows (don't close them with the X, since that will not save the changes!)
Now we look at the other types of text.
This can be found in the tabs from 'Favor Dialogue' to 'Misc'.
Since Favor Dialogue doesn't hold anything in this patricular 'quest', we go to the tab 'Detection'.
1. Open the tab Detection
2. Select 'AlertToCombat' in the topics block. (middle one)
3. Double-click 'Now you're mine!' in the right block.
4. Double-click 'Now you're mine!' in the Response Text block and translate and retype it in the new window.
If you don't feel like making the actual mod, you can look up the text and translate it. If you give me the translation following the scheme below, then I can incorporate it into a mod.
EditorID: DialogueGeneric
Tab: Detection
Subtab: AlertToCombat
English text: Now you're mine!
Dovahzul translation: Nu hi los dii!
If you still have questions, let me know!