It depends, if they are Avery or another common brand then you need to find the associated number, normally on the front of the packet. If your using Word (bit of an assumption but 95% of people will be) then go to teh Tools menu and select the Envelopes and Labels option. Then click on labels and then select options you then need to find your label from the list. If you dont have the number then the packet should have the size information, to enter this select 'Details' and type them in. If you dont have the packet then get a ruler and measure the labels and enter this information in. use the diagram as a guide to what each section requires. Once you have done one of these then select 'New Document' and a new document will open with a grid which hopefully correspond to your label sheet. Some printers can be a bit off so best bet is not to use the extreme edges of the labels.