How do put the cutting cord on the spool so that it can be pulled out after wearing down

Hi, Robert I will try to explain the best I can. There are many different ways the manufacturers build the heads and spools for grass trimmers. Remove the spool from the head of your trimmer. Some just pull out, while others have different ways and adapters that screw out, if you have never removed yours look in your owners manual or if you don't have a manual you will have to find the way you remove the spool from the head. When you remove the spool, remember which way it goes.back in. Once the spool is removed if there is still a small amount of line remaining observe the way it is held on the spool. If no line remains look at the bottom of the spool for an eyelet or holes right at the bottom or on the side. If you see an eyelet just tie the line to it. If there is nothing but one hole that means that with the right size of line it will go in tight to hold line. If 2 holes are present insert in one hole and out the other. If you have a 2 line trimmer then 2 holes means in one hole and out the other which makes sense. Whatever is the way to hold the line in, sometimes it just doesn't hold the line on once you start winding line on. There are a few manufacturers I find you can use on all spools and is easy.Take some packing tape or any kind of tape you want to use. Wrap around line then tape to bottom of spool, the easiest way to hold on and works on any make of trimmer. Look at the spool and there is usually an arrow on outside to give you the direction to wind. It is important how you wind line on spool, try to wind neatly like back and forth in even rows so that later the line doesn't get tangled up. But it is also very important not to twist the line. What I mean by that is the way the line comes off the package it comes in. Wind the line the same way it is wound on pack. I hope I am explaining it properly and that you understand what I mean. Put the spool and pack end to end and unroll the line out of the pack the same it is rolled in the package. That is to prevent the line from getting always tangled up and you having to remove the spool to get untangled. I think you probably get what I mean. Do not put too much line on the spool, leave about 1/4" from top of spool. Install the spool the exact same way it came off. I hope I have helped you and that you understand the way I explained it. All the best and good luck. I will gladly answer any other questions.