it depends how liginified the stems are. some strains have branches with a tendency to split away from the stem if tied too late. gently bend the stem back and forth until you feel it start to soften up. once the stem feels flexible try to bend it into place. watch for breaking and splitting and make sure the bark doesnt tear away from the branch. when you tie it be sure the tie doesn't circle the branch or it could become girdled as it grows. use something thick and soft to tie it. i use bonsai wire but its very expensive, coated 16awg solid core wire works well also. hemp string is also a popular choice. i don't like strings because they can hold water, try to never use yarn.