The basic schematic of a voltage to current converter looks like this
The values are nor correct for what you want, they are for very low currents, also a rail to rail opamp would work better and you will need the R2 to be about 100 ohm.
The main idea of the operation is that the opamp constantly compares the voltage in the positive input with the voltage in the negative input which is coming from the voltage drop on R2.
Depending on the output current you get more or less voltage drop on that resistor (it works like a shunt resistor) but when this voltage is different from the voltage of the positive input the opamp drives the transistor with higher or lower current to equalize these two voltages.
An example, suppose that R2 is 100 ohm, for 10mA the voltage drop on the resistor will be 100*0.01=1v, if you set the positive input to 1v then the circuit will automatically balance so that the output current becomes 10mA so that both plus and minus opamp inputs have the same voltage (1v).
the above circuit uses a pot to set the positive input voltage, if you want to feed it a voltage coming from another source then it is not needed.
Alex