Premarin is available in a pill or cream form. If you are taking the oral form, which comes in a variety of dosages, you take it once a day, with or without food. Like many other medications, it's a good idea to take it the same time everyday so you don't forget.
If your doctor has prescribed Premarin cream you may not need to use it every day. Some women only need to use it twice a week and some women take it in a cyclic fashion, daily for 21 days and then off for 7 days. Your doctor will tell you what is best for you. It comes with an applicator that you fill and insert into the vagina. When you get the tube it will have an instruction pamphlet showing you how to apply the cream. Essentially, you will thread the applicator onto the tube and squeeze the tube with the medicine from the bottom until it fills the barrel. There will be a line that tells you when to stop. Then you insert it into the vagina, depress the plunger to release the medicine, similar to inserting a tampon.