so, this is my first mod, and i would like a little help. This mod is supposed to set the Necromancer birthsign and class as playable, as well as extending the 'reanimate' spell time. i've got the class and spell time to work, just not the birthsign. what can i do to get this to work?

http://cs.elderscrolls.com/constwiki/index.php/Birthsigns

It's an odd little bug: sometimes a birthsign just doesn't show up. It's probably something to do with the FormID. The solution, oddly enough, is to just make several copies of the birthsign within the mod. Rename them (Necromancer1, Necromancer2, etc.) so you can tell which is which, then see which of them actually shows up in the game. Pick one that does, strip the number off the name, and delete the rest.

In the CS are you creating the birthsign by going to the Character>Birthsigns option in the toolbar menu? If not, open up the Birthsigns window (through the mentioned CS menu option) and move the window to the side so it's not covering your "Object Window". In the Birthsigns window under the Birthsigns column, right click and select "New" from the context menu. A "New Form Editor ID" window should show up. Give the new birthsign whatever ID name you want (this is the CS editor ID, not the name that will show up in game) and click OK. Then the new ID you gave it should show up under the Birthsign column in the Birthsigns window. Click on the ID you made so that it's the highlight/ active one to edit out of the Brithsings column. From there to the right of the Birthsings column, fill out the Full Name field (this is the name that will show up in game) and the Description field if you want. Now go over to the Object Window, expand the Magic heading in the far left column and then click on the Spell sub heading and find the NPC birthsign ID you're trying to make playable (AbBirthsignNecromancer?). Click and hold on its ID name and drag it over to the Spell field of the Birthsigns Window and let go of the mouse click. That spell should now show up under the Spell field of the Birthsign Window. Click OK on the Birthsign Window and save your ESP file.

As for the Constellation Image file, that's a whole other exercise in which you need some sort of BSA Commander program/ tool to extract the in game Constellation Image files and put them into the correct folder under your Oblivion/ Data Files directory, before you open up the CS set again to work on your ESP file further (if you want your new birthsign to have a Constellation Image).

Hope that is somewhat helpful.