Step 1 of 7
Cross
Make a white cross on the bottom face, each edge lined up with the centre of its side. Hold the cube yellow on top, then for each white edge, turn the whole cube so that the centre of its other colour is in front, and apply the matching basic situation. An edge stuck in the middle with white in front, or misplaced at the bottom, first goes back up to the top (R U R' from the middle right, L' U' L from the middle left, F2 from the bottom): it then becomes a basic situation.
The basic situations
Hold the cube as the hint says, then apply the formula. In the app, every formula is animated on a virtual cube.
On top, white up
The edge is on top, white facing up: turn U until it is at the front, its other colour above the front centre.
F2→ piece in placeOn top, white in front
The edge is on top, white on the side: turn U until it is at the front, white facing you.
U' R' F R→ piece in placeMiddle right, white on the right
The edge is in the middle layer, front right, white on the right face.
F→ piece in placeMiddle left, white on the left
The edge is in the middle layer, front left, white on the left face.
F'→ piece in place