I would suggest you to regularly check the official website of IET Lucknow for updates regarding admission dates. IET generally releases the admission dates around the time of JEE-Mains and the start of the academic year.
For the current academic year, admissions will be done on the basis of JEE-Main scores. The JEE-Main registration date started on November 30, 2023. After that JEE-Mains 2024 exam was held on January 24 - February 1, 2024. The 2nd session was held on April 1- April 15, 2024. The tentative dates for UPTAC registration and counselling for admission to BTech is around July, 2024 - October, 24.