After taking your shahada first thing to do is purify himself by taking a complete bath (Ghusl) and then correcting the Faith.
in Islam, Faith stands on six pillars and first things first for a muslim is to believe in these six terms of Faith also a Muslim should not spend time without Ghusl.
Ghusl simply renews our state of purity in front of Allah. Ghusl is obligatory in certain events. If these events happen you need to take ghusl again.
Here is six pillars of faith a muslim must accept and believe in all of them.
Allah exists and is the only Creator, Sustainer, and Planner of everything in existence.
Mankind was created to dedicate their worship for Allah.
Allah is the only one who has right to be worshiped.
Angels exist, that they are the creation of Allah, and that some of them have been given names. (Jibreel and Mikael etc.)
The duty of angels is to serve and obey God in every command, and they never exceed God's laws and orders.
in Islam, it is an obligation to believe in all divine Messengers. Leaving off believing any Prophet or Messenger constitutes to disbelief in Islam.
A Muslim must believe in all the prophets sent, including those whose names have been reported to us and those whose names have not been reported to us.
There are 25 messengers who have been mentioned by name in the Qur’an and there are many not mentioned in Qur'an, a muslim must believe all of them without leaving even one.
In Islam, it is a part of faith to believe all the books and scriptures (original versions, not the versions existing today) that were revealed to the prophets.
Allah sent those Books to the followers of specific Prophets until those books are corrupted and modified by people.
Allah sent down the Quran as a last Revelation and Guidance for humanity.
Scriptures
Onye Alakụba ga-ekwe na e nwere ndụ ọzọ mgbe ọnwụ gasịrị na ndụ mgbe ọnwụ gasịrị dịịrị n’ebeebe.
Ikwe na Akhirah (Ndụ Mgbe Ọnwụ) gụnyere;
Allah adịghị n'oge na Allah maara ihe niile site na mmalite ruo n'ebeebe. Allah maara ihe ọma na ihe ọjọọ niile ga-eme.
Allah enyela mmadụ ihe ọchịchọ na ọ maara ihe mmadụ ga-eme na ọchịchọ ya. Allah adịghị enye mmadụ ihe niile nke ọchịchọ ya, ụfọdụ ihe adịlarị kpebiri site na ya. Dị ka onye ga-abụ ndị mụrụ gị, elu na ọdịdị gị wdg. Ihe niile anyị na-eme na anyị ga-eme edereala n'ihi na Allah adịghị n'oge na Allah maara ihe niile.
Ihe atụ dị mfe nke nghọta ọdịmma na Islam bụ, anyị enweghị ike ịhọrọ nne na nna anyị, nke a bụ ọdịmma e nyere site n’aka Chineke. N’aka nke ọzọ, ime ma ọ bụ na-eme ihe iwu na-akwadoghị nwere ike ịdabere na ọchịchọ mmadụ; Chineke kwere ka ọnọdụ abụọ ahụ mee na O maara ma mmadụ ga-eme ihe iwu na-akwadoghị ahụ ma ọ bụ na ọ gaghị eme.
Onye Alakụba ọhụrụ ga-amalite ime Islam dịka o nwere ike, mgbe ọ sachara onwe ya site n'itinye aka Ghusl na ikweta ọkpụkpụ isii nke Islam.