OK.

To change the key signature within a song:

Go to the measure where you want the new key signature
Press F5 to bring up the Bar Settings dialog
In the fourth row down (at least, in version 2013), use the pull-down "Key Signature Change to" to select the new key signature
You will see only a red box, indicating a change has been made there, but if you go to the Notation Window or the Leadsheet Window, you will see the key signature

To change the tempo within a song:

Go to the measure where you want the new tempo
Press F5 to bring up the Bar Settings dialog
In the second row down (at least, in version 2013), use the entry box for "Tempo Change To"
Alternatively, use the third row down to enter a percentage change

For more help, hover your mouse over any of these and read the tool-tip.

If you make one of these changes with F5, don't forget you may need to go to another measure to 'change it back'.

If you upgrade to version 2013, a handy new feature in the Memo can list every change made by F5 in your song.

BIAB 2025 Win Audiophile. Software: Studio One 7 Pro, Swam horns, Acoustica-7, Notion 6, Song Master Pro, Win 11 Home. Hardware: Intel i9, 32 Gb; Presonus 192 & Faderport 8, Royer 121, Slate VSX, Adam Sub8 & Neumann 120 monitors.