Every Indian citizen staying in a foreign country, who has not acquired citizenship of a foreign country and has completed 18 years as on 1st January of the year, can make an application in form 6 A for registering in the voter roll for his/her constituency (place of residence in India as mentioned in the passport). The application can be presented to the concerned Electoral Registration Officer (ERO). Particulars and addresses of these EROs and form 6 A, along with guidelines for filling up the form, can be obtained from the official website of the Election Commission of India http://eci.nic.in.
The application forms should be sent directly to the EROs of the constituency. Documents to be submitted with the application form include one recent passport size colour photograph (with a light background and showing the full face of the applicant), self-attested photocopies of relevant pages of passport containing the photograph and all other particulars of the applicant as also the page containing a valid visa.
Once enrolled, the Indian national living abroad will be able to cast vote in the election in the particular constituency for which one would have to be physically present on the day of election at the polling station along with the original passport. Please note that there is no provision of voting by post, or voting at Indian Missions abroad or online voting.