What do you need to do with it? If you want a numeric variable to display with a binary format, select Properties>>Numeric Format>>Type>>Binary (uncheck Show Radix Prefix). If you want to get the binary representation of a number in a string, assign it in an expression like locals.string = Str(locals.num, "%b"). If you want to pass the actually binary bits to a dll parameter, that is what TestStand does already.
Note that when you enter a number in a variable value or an expression, you can use a radix prefix. For example you could type 10, 0xA, or 0b1010.