NEVER work from a master, make a copy of it and work with the copy.
That way, if you don't like the end result, you can easily start again and nothing is lost.
If at all possible, work at 16 million colors and reduce only when you're done.
First, crop your two pics to equal size and save as masters.
Next, open a new graphic (we'll call it "C") that is the same height as your pics but is twice the width.
Copy "A" and paste to one side of "C".
Next, copy "B" and paste to the other side of "C".
You now have a single graphic with "A" on one side and "B" on the other.
If you want a divider between, add 3-5px when you create "C". (the width of "A" plus the width of "B" plus an additional 3 to 5 px) and slide the "B" over to the side.
You can now add borders to the outside to 'frame' it.
That way, if you don't like the end result, you can easily start again and nothing is lost.
If at all possible, work at 16 million colors and reduce only when you're done.
First, crop your two pics to equal size and save as masters.
Next, open a new graphic (we'll call it "C") that is the same height as your pics but is twice the width.
Copy "A" and paste to one side of "C".
Next, copy "B" and paste to the other side of "C".
You now have a single graphic with "A" on one side and "B" on the other.
If you want a divider between, add 3-5px when you create "C". (the width of "A" plus the width of "B" plus an additional 3 to 5 px) and slide the "B" over to the side.
You can now add borders to the outside to 'frame' it.