In order to perform Umrah or Hajj, a Muslim man or woman has to enter the Ihram. Without entering the Ihram, one's Umrah or Hajj cannot be performed. Ihram is the sacred state in which men and women carry out the required rituals to complete Hajj or Umrah. You also have to wear special clothing that is designed for the purpose of performing Umrah or Hajj.
Men's Ihram differs from that of women. While men's Ihram is two sheets of white clothes that leave some parts of their body unclothed, women's Ihram is a dress that completely conceals them, leaving their face and hands revealed. A woman cannot cover her face because that is prohibited during pilgrimage.
Upon entering the Ihram, a woman is recommended to perform Ghusl (purification bath). It is important to make the Niyah (intention) of bathing for Ihram. However, in case adequate water is not available for Ghusl, one can perform Wudu (ablution) and continue their Hajj/Umrah rituals.
Women are also allowed to wear regular clothes if Ihram is not available. It has to be made sure that the clothes which are worn with the intention of entering Ihram have to completely cover the body of the wearer, leaving hands and face uncovered.
It is also recommended that both men and women offer two Rakah (Salah) with the Niyah of assuming the state of Ihram. Every pilgrim should know that the ihram has to be worn before passing the Miqat (the place from where ihram starts). Al-Bukhari states that Prophet Mohammed (PBUH) said: "one shouldn't pass the Miqat unless he/she is in the state of Ihram." (Al-Bukhari)
Lastly, one should avoid the acts that are prohibited for a person who is in the state of Ihram, such as wearing Attar (perfume), wearing makeup, wearing socks et cetera. May Allah (SWT) give us the opportunity to go into Ihram during Umrah and Hajj dates and only come out of it after performing Umrah or Hajj (Amen).