It's simple you just have to pick up you weight (W) and you height (H) but
Weight in kilo gram (kg)
Height in meters (m)
[tex]BMI=\frac{W}{H^2}[/tex]
for an example a person that weight is 100 kg and height is 1.80m
Using this formula
[tex]BMI=\frac{100}{(1.80)^2}[/tex]
[tex]\boxed{\boxed{BMI\approx30.86}}[/tex]