Open the program and import the mastered midi track or stereo audio track that you're going to be changing the bpm on. Click the "Track View" on the left of the imported track to expand and display all settings up close.
Click the "Fixed Tempo" button located at the bottom right hand corner of the screen.
Press the spacebar to preview the song then find and click your start position for the tempo change in the left "Track Edit" window. Line the start position at the beginning of the selected loop of the song, if only editing a part of the song.
Locate the "Tempo Change" window on the right of the screen and drag the mouse cursor up or down the paremter blocks to change tempo, then click the left mouse button to set your tempo. Drag the cursor towards the top of the screen to slow your tempo or drag towards the bottom to speed up.
Press play or the spacebar to preview the tempo change.