If you click 'No', the editor will ask you if you want to quit the application, but I don't recommend you do that unless you feel like loading everything again.) (If you want to take a look at them you can click 'Yes' to each of them.
These 'default' warnings are harmless and won't affect your mod so you can safely skip past them by clicking 'Yes to All'. This is the first of several warnings that you will get every time you load the editor (they're mostly about doors). When the editor is finished loading the game data, you will likely see a warning alert box pop up informing you about a navmesh error. Depending on your machine and the alignment of the stars it may take a half a minute to a couple of minutes to load everything.
Otherwise, open the editor if it's not already open, select the Skyrim.esm and Update.esm in the Data browser (File, Data., double-click Skyrim.esm, double-click Update.esm, OK) as shown in the starter tutorial on the wiki and load the game data. If you created a mod in the starter tutorial and still have it open, close it now.
