Upvote:2
You need to apply for a normal, short stay visa. The purpose of your trip (question number 21) should be "OTHER" and you should type "Academic Conference"; as none of the choices apply. These are:
- Tourism
- Business
- Visiting family or friends
- Cultural
- Sports
- Official Visit
- Medical Reasons
- Study
- Transit
- Airport Transit
- Other
You can provide the invitation letter as part of your supporting documents; along with the normal requirements for such a visit:
- Proof of financial means / support
- Hotel accommodations for the period of your stay
- Travel reservation for the period of your stay
- Insurance suitable for Schengen visa purposes and valid for the period of your stay.
- Valid passport
- Letter of employment (if applicable)