You may want to review solving easier radical equations first.
If there are more than one root in the equation, you need to be more careful, but it's still basically the same idea. Just get one of the roots by itself on one side. Then, when you square both sides, it will be gone! Keep going like this until they all disappear.
For example, suppose you have to solve √(x + 3) + 1 = −√(x − 2). Since you have a radical by itself on the right (constant factorsa are okay), you square both sides, getting x + 4 + 2√(x + 3) = x − 2. Now you need to get the remaining radical by itself, so you move stuff around, ending up with √(x + 3) = −3. Now you square both sides again, getting x + 3 = 9, so the only possible solution in x = 6. Checking (which you still have to do) reveals that it doesn't work, so there's in fact no solution.