Hey guys this is my first thread so please ignore the mistakes i have made
Requirements :
A photoshop Software
A computer
Some time
Steps
1.Firstly working with the photo that has the background that you want to use, Select the whole thing (Select>All), Copy the whole thing (Edit>Copy), and then working with the photo that has the foreground that you want to use, Paste the previous photo onto a new layer (Edit>Paste). Your layers menu for the for your photo should now look similar to the picture to the left. With the background photo on top of the foreground photo.
2.Now, add a Layer Mask to the upper layer that Hides All, (Layer>Add Layer Mask>Hide All). Your Layers menu should now look like similar to the picture below.
3. Click on the Brush Tool
4. Then (with the mask on the upper layer selected) simply brush where you want the new background to show through. You will probably have to change brush sizes often for the more intricate places.