When the rebels take strain in the campaign to move extra spaces, do they have to spend a action to move, then take strain to move, or can they just take 2 strain to move 2 spaces or take 1 strain for 1 space. Also, can they take 2 strain to move over friendly figures?

Taking strain to move 1 point is not considered an action. They could spend 2 strain to move 2 spaces then perform 2 actions like attacking twice if they wanted.

Thanks that is a lot clearer

Per the RRG. The underlined emphases is mine, the bolded text is that way in the RRG.

A hero can suffer 1 strain at any point during his activation to gain one movement point. He may do this up to twice per activation.

So you could take 2 strain, move 2 spaces, then attack twice. Or take 1 strain move 1 space, attack, take 1 strain, move 1 space, then attack. Movement isn't an action.

Again, this part is helpful:

Performing a move does not move the figure ; it only provides movement points that may be spent during that figure’s activation. This means that a figure may use its first action to perform a move, followed by an attack, and then spend the movement points. It may even spend some movement points before the attack and then some of them after the attack.