There are two aspects to freedom of religion. These are the freedom to do whatever you want in your religious practices and beliefs and the freedom from having the government impose a religion on you. Both of these are parts of religious freedom as we conceive of it in the United States.
One aspect of religious freedom is “free exercise” of religion. This means that the government cannot prevent you from holding certain beliefs or from practicing your religious rituals. Of course, there are some limits to this. For example, you cannot conduct human sacrifices even if you do have the right to believe that they are necessary. Outside of such extreme things, however, freedom of religion means that you can act as your religion tells you to. It also means (without qualification) that you can believe whatever you want.
But there is also the freedom from established religion. What this means is that, at a minimum, the government cannot tell you that you must join a particular church. It cannot use your money to support a particular church. In other words, government may not support a particular religion.
Thus, freedom of religion includes both the freedom to do what you want and the freedom from being required to support a particular church.