If I am following a recipe that is using cup measurements do I just put the butter into the required cup?
In the US butter can be measured in cups but measurements are often also given in "sticks". Butter is mostly sold in packages of 1/2-pound or 1-pound and within these packages the butter is split into pre-wrapped sticks weighing 1/4 pound (or 4 ounces/110g) each, which also equals 1/2 cup. The wrapping on each stick indicates tablespoon measures (8 tablespoons per stick).
So if you are using cup measures you could pack the butter into a measuring cup or below is a ready reckoner which may help if you have scales.
1 tablespoon butter = 1/2 ounce/15g
1 stick butter = 8 tablespoons = 1/2 cup = 4 ounces/110g.
2 sticks butter = 1 cup = 8 ounces/225g.