Oh began his study of hapkido at Ji Han-Jae (지한재)'s first hapki yukwonsool school, the An Moo Kwan (안무관) in Andong, Gyeongsangbuk-do.

Fellow students were Kwon Tae-Man (권태만), and Yoo Young-Woo (유영우).

Oh joined other senior practitioners already training in Seoul at that time, early hapkido practitioners Hwang Deok-Kyoo (황덕규; latter day president of the Korea Hapkido Association), Myung Kwang Sik (명광식; latter day founder of the World Hapkido Federation), Lee Tae Jun (이태준), Kim Yong-Jin (김용진; founder of the Ulji Kwan), Kang Jong-Soo (강종수), and Kim Yong-Whan.

By 1983 Oh Se-Lim, with political problems and many of the original founding members of the Korea Hapkido Association departing (Ji Han-Jae, Myung Jae-Nam), renamed the association by the name first used by the organization he had first been a part of with Master Ji, the Dae Han Hapkido Hyub Hoe (대한 합기도 협회), with a new preferred English rendering; the Korea Hapkido Federation (KHF).

Master Oh resigned the position of the president of the KHF, that was succeeded by Kim Jong-Yoon (김종윤) in 2008.