Query: How can a person be a Muslim?
A man converts to Islam by sincerely pronouncing Shahada. He doesn’t embrace Islam by performing acts of worship nor other Islamic rituals.
As for Ghusul (washing up), it’s preferable for whoever converts rather than an obligation. Messenger of Allah (peace be upon him) said, “He who professes La ilaha illallah (There is no true god except Allah), and denies of everything which the people worship besides Allah, his property and blood become inviolable, and it is for Allah to call him to account”. [Muslim].
Then, the new convert is obliged to perform acts of worship and rituals just like all other Muslims.
It’s advisable for Muslim converts to read about Islam and its rulings and creed in a simplified language.
S/he should also read the biography of the prophet (peace be upon him) and his companions.
It’s also advisable if the convert lives in a country where there’re calls against Islam to read the refutations of these allegations written by distinguished Muslim scholars so that none can shake their belief or raise doubts in their heart.
And Allah knows best.
Sources: Al-Azhar Al-Sharif
Also, Read: Swearing by other than Allah