I copied this for you ( I'm too lazy to write it all out)
For making 1l of a basic, mild 0,5% neem oil spray,
you will need:
1-quart (1l) of warm water
1 teaspoon (5ml) of neem oil.
⅓ tsp (1-2ml) of mild liquid soap, insecticidal soap or another mild detergent.
Other sources say that 1 tsp of soap is also fine.
Mix water and soap in a closed bottle and shake well so the soap is fully dissolved. Add the neem oil, and shake again.
The concentration of 0,5-1% is the most common for general and regular garden use, although you can experiment with 2% sprays if you think you need a stronger solution.
https://www.trees.com/gardening-and-landscaping/neem-oil this link will take you to the site