How can I use the command shl to shift 1 by a variable?
mov one, 1
shl one , eax
Returns an error.
You can shift only shift by cl, unless you use BMI2 shifts. So for example:
mov edx, 1
shl edx, cl
Since you're shifting the value 1 to the left, there is an other applicable instruction: bts. bts can take any register as index.
xor edx, edx
bts edx, eax
Be careful when using it with a memory destination, the index won't be reduced modulo 32, so you can use it to (accidentally) set a bit quite far away from the base address.