2. You want to put the soccer player onto the text image. So you first of all have to resize the text image (but not scale). To do this activate the text image and select  Layer/Layer info. The information dialog appears. 

Here you can change the size of the image. If you increase the size, there will be a border on the right side and on the bottom of the image, filled with the background color. 

3. Now you have several ways to bring the soccer player to the text. 
- you can create a lasso and drag the player to the text image. When you release the mouse button over the text image you get a selection with the soccer player. Now you can place the player and then double click on it to put it in the text layer. You can also select Layer/Convert Selection to Layer to get a new layer with the soccer player. 
- you can select the layer move tool and move the whole soccer player to the text image. You will get a selection on the text image like before. 
- you can activate the soccer window and press Ctrl+C to copy the image. Then activate the text image and press Ctrl+E or select Edit/Paste as selection. You will get a selection like before.