The concepts of calling functions, passing parameters, and returning a value are part of the 'C' standard; however, the specific way in which a particular compiler implements them is entirely down to that compiler - it is Implementation-defined

This means that you are going to have to refer to the Documentation for your particular compiler to find out how to make calls between 'C' and assembler.

If you are also using some sort of development environment to manage your project, you are also going to have to refer to its Documentation to see how to do it.

If you want specific help with the particular tools that you are using, you are going to have to state what they are - give full details of the tool names, tool author, and tool versions

Having certain parts of a mainly-'C' project in assembler is an extremely common thing - especially in embedded systems.
Therefore, if your tools don't document this, you should seriously consider abandoning them in favour of ones that do!