Membership costs €8, memberships are by academic year and you can apply for membership for the coming academic year from June onwards.
Note: when you join the guild, your quota for events is Ist year (freshers) by default (applies also to exchange students) except for IEM Master's freshers, where the quota is IV by default - according to the guild's queue decree, you can apply for a change if you have eg studied another field before. You can request this change already in the membership application "Why do you want to become a member?" by mentioning what quota you would want to be and why.