To calculate your horoscope chart, you will need to look up in an atlas the latitude and longitude of your town or city of birth; and if you want an accurate horoscope chart with the exact Ascendant, Midheaven, House Cusps and Moon position, you will need to include your exact hour and minute of birth in the calculations.
If you can provide a fairly accurate birth TIME when you order your horoscope chart, you will get accurate information about the degree and Sign of each of your House Cusps, your Midheaven and Ascendant (and Rising Sign), the Sun and Moon and all the Planets, and your North Node of the Moon and your "Fortuna" (or "part of Fortune"); plus a list of all the Aspects between the Planets in your birth horoscope, including Aspects to the Midheaven and Ascendant and North Node. The House System used is the Placidus System, and your chart will note the exact "Sidereal Time" (star time) which has been accurately translated from your local clock time on your birthday at the place of your birth.
Sidereal Time is calculated from the "Universal Time" (UT) mentioned above; and UT is based on translating the local clock time at the place of birth to the equivalent time at Greenwich, England (GMT). The calculations involve adjusting for Time Zone, and also for the distance between the Longitude line used for that Time Zone and the actual longitude of the place of birth. All these calculations are based on the daily (diurnal) rotation of the Earth, since how the Sun and Planets appear over your own place of birth depends on the rotation of the Earth itself, which is what determines the time of day.
Tables of planetary positions are referenced to their positions over Greenwich at a certain time of day (usually Midnight or Noon); so to find their positions at another place on Earth, we have to translate the local time to the time at Greenwich, which is called Universal Time. When the time of birth is not Midnight or Noon, we extrapolate the planetary positions at that time by moving them the same proportion of their motion over the next 24 hours, as the birth hour (and minute) is a fraction of 24 hours from the reference time of Midnight or Noon on that day. For example, if the birth time is 6:00 AM, that is 6/24ths of the day; so the planets will have moved 6/24ths of the distance from their position at 12:00 AM Midnight to their position at Midnight the next day.
The Sun and Planets have their own paths of motion relative to Earth, and the rotation of the Earth does not affect their positions. We only need to know the time of day to be able to figure out what time of day it is at Greenwich, for the positions of the Planets at Greenwich have been calculated for a every date at Midnight and/or Noon Greenwich Time. Books containing tables of planetary positions, called "ephemerides" (the singular form is "ephemeris") have been created using Greenwich as the point of reference; and computer programs which calculate planetary positions for any date and time also use Greenwich as the standard reference point. Nowadays, a computer program uses complex astronomical equations to create the data in the emphemeris itself.
After calculating the positions of the planets at birth, we then proceed to calculate the positions of the twelve House Cusps. Again, we adjust the local time to Universal Time, and then refer to a Table of Houses. This table lists the position of a Point called The Midheaven on various dates for each degree of latitude north or south of the Equator. From the point of the Midheaven, another point called The Ascendant is determined, and then their opposite points of The Immum Coeli and The Descendant are known, since they will be exactly 180 degrees away. Those four Points are basically the same in all horoscope charts, and they form the cusps of the 1st, 4th, 7th and 10th Houses. What may differ is how the remaining House Cusps are determined, depending on what system of House division is used. Some commonly-used systems are the Placidus and Koch systems, and they place the intermediary House Cusps at slightly different points.