How to add one missing schematic?
If it is just one or a few, post as many details as possible in the schematics forum.
Post a screen shot of the schematic from your datapad, there it has some small details read nowhere else.
How to submit a few missing data?
If it is just a limited amount of data, post that as a comment in the comment field at the schematic. Then moderators and schematics maintainers can edit/update that schematic.
Or post the data at the forum mentioned above.
How to be more active with schematics
Quite some time ago it was made possible for SWGCraft members to become schematics maintainers. This makes it possible to add/edit/complement schematics.
There is a guide for maintainers, not that it is complex or very hard, but in case there are some questions they have an answer -- I hope.
You must apply for this service, may I suggest this topic. Not that the moderators and developers here are that picky, none has been denied this far...

Remember that once a schematic is updated it takes up to 24 hours until SWGAide has obtained the new data. If there is anything to update SWGCraft compiles the data 01:00 AM UCT (GMT). SWGAide communicates with SWGCraft about new schematic data when it is launched (in a future I will improve this).
You applications are welcomed, as well as any submissions you may have

/Zimoon