This Shabbat is Shabbat Mevarchim ("the Shabbat that blesses" the new month): a special prayer is recited blessing the Rosh Chodesh ("Head of the Month") of the upcoming month of Nisan, which occurs tommorow (Sunday).
Prior to the blessing, we announce the precise time of the molad, the "birth" of the new moon. See molad times.
It is a Chabad custom to recite the entire book of Psalms before morning prayers, and to conduct farbrengens (chassidic gatherings) in the course of the Shabbat.
Exodus 35:1–40:38
Moses assembles the people of Israel and reiterates to them the commandment to observe the Shabbat. He then conveys G‑d's instructions regarding the making of the Mishkan (Tabernacle). The people donate the required materials in abundance, bringing gold, silver and copper; blue-, purple- and red-dyed wool; goat hair, spun linen, animal skins, wood, olive oil, herbs and precious stones. Moses has to tell them to stop giving.
A team of wise-hearted artisans make the Mishkan and its furnishings (as detailed in the previous Torah readings of Terumah, Tetzaveh and Ki Tisa): three layers of roof coverings; 48 gold-plated wall panels, and 100 silver foundation sockets; the parochet (veil) that separates between the Sanctuary's two chambers, and the masach (screen) that fronts it; the Ark and its cover with the Cherubim; the table and its showbread; the seven-branched menorah with its specially prepared oil; the golden altar and the incense burned on it; the anointing oil; the outdoor altar for burnt offerings and all its implements; the hangings, posts and foundation sockets for the courtyard; and the basin and its pedestal, made out of copper mirrors.
An accounting is made of the gold, silver and copper donated by the people for the making of the Mishkan. Betzalel, Aholiav and their assistants make the eight priestly garments—the ephod, breastplate, cloak, crown, turban, tunic, sash and breeches—according to the specifications communicated to Moses in the Parshah of Tetzaveh.
The Mishkan is completed and all its components are brought to Moses, who erects it and anoints it with the holy anointing oil, and initiates Aaron and his four sons into the priesthood. A cloud appears over the Mishkan, signifying the divine presence that has come to dwell within it.
Exodus 12:1–20
This being the Shabbat that falls on or before the first of Nissan, we also read the section of Hachodesh (Exodus 12:1–20), which relates G‑d's words to Moses in Egypt two weeks before the Exodus, instructing us to set the Jewish calendar by the monthly new moon, and to regard Nissan as the "head of months." G‑d also instructs to bring the Passover offering, to eat it with matzah and bitter herbs, and to abstain from leaven for seven days.
Ezekiel 45:18-46:15 {Hachodesh}
This special haftorah is a prophecy regarding the Paschal Offering that will be brought during the Messianic Era, reflecting the theme of the Hachodesh Torah reading—Moses' command to the Israelites in Egypt to prepare and bring the Paschal lamb.
This haftorah is part of Ezekiel's prophecy regarding the third Holy Temple—its structure, inauguration and some of the practices that will be observed therein.
The haftorah begins with a description of the various sacrifices that will be offered during the Temple's seven-day inauguration ceremony, and then mentions that on the 14th of Nissan we shall bring the Paschal offering.
Much of the rest of the haftorah is devoted to the sacrifices that will be brought by the "leader," and prescribes his entry and exit from the Temple.
What blessing was to be recited by one who beholds the new moon, in the period when Israel used to sanctify the new month? Some of the sages hold: "Blessed be He who renews the months." Others say: "Blessed be He who consecrates the months." And others say: "Blessed be He who hallows Israel," since unless Israel sanctify it, it is not sanctified at all.
(Midrash Rabbah)
https://www.chabad.org/parshah/in-depth/default_cdo/aid/74478/jewish/In-Depth.htm