This is the 1st we've heard of a RMD. How would we go about withdrawing funds prior to 1 Apr?

Where did you hear about RMD?  Did you turn 73 in 2024 and need to start taking the RMD Required Minimum Distribution from a IRA or 401K accounts?  Or are you getting pensions?

For pension.....It's whatever they send you. Say all of it is the RMD. If you have a RMD requirement it will ask you if it is the RMD. Say yes and enter the amount as the RMD amount. The pension doesn't need to calculate any RMD. Anything your pension pays you is considered to be the RMD. Traditional pensions automatically fulfill the rules of an RMD. So just enter the same amount in box 1 for the RMD for each 1099R. 

RMD INFORMATION

IRS Pub 590-B, page 7, Required minimum distributions (RMDs).
Individuals who reach age 72 after December 31, 2022, may delay receiving their RMDs until April 1 of the year following the year in which they turn age 73.
https://www.irs.gov/pub/irs-pdf/p590b.pdf

IRS Pub 590B https://www.irs.gov/pub/irs-pdf/p590b.pdf says…….
Your required beginning date. The date you must begin receiving RMDs is determined by the date you reach age 72. See the following to determine your applicable required beginning date.

Age 72 after December 31, 2022. If you reach age 72 after December 31, 2022, you must begin receiving required minimum distributions by April 1 of the year following the year you reach the age 73.

Age 72 in tax years 2020, 2021, or 2022. If you were born after June 30, 1949, you must begin receiving required minimum distributions by April 1 of the year following the year you reach age 72.

Age 70 ½ for tax years 2019 or earlier. If you were born before July 1, 1949, you were required to begin receiving required minimum distributions by April 1 of the year following the year you reach age 70 ½.