An "conditional" or "if -clause" has two parts: The "If part" and the "main" part. The "if

-part" always shows the condition
that needs to be true for the main clause to become reality:
If part
|
Main part
|
If it rains tomorrow,
|
we will watch TV.
|
|
we can watch TV.
|
|
watch TV!
|
If + Personal pronun + Simple Present + rest
|
Personal Pronoun + will future + rest.
or can/must/etc.
or Imparative
|
You can swap the if-part and the main part:
If it rains tomorrow, we will watch TV.
OR
We will watch TV if it rains tomorrow.
But: If your "If-part" is first, you must put a comma behind it.