How do you

How do restring a string trimmer?

We need more information such as make and model. The very, very basic answer is remove the spool from the shaft. There is usually a locking pin in the shaft bnear the spool to allow unscrewing the sppol. Once it is off you can buy a prefilled spool or try to wind new string yourself. At this point I need the model to go further. Do you have the manual?