An importance score is associated with each attribute and summarizes how much impact the attribute can have upon choice (given the range of levels you included in the study). Importances are computed (for each respondent) by percentaging the ranges for attributes. Thus, they sum to 100. Note that you can change the importance of an attribute by just picking a wider or more narrow range of levels when designing your conjoint study, so importance scores should be interpreted with caution.
Download Individual-Level Importance Scores
You can download the importance scores for each respondent, for your attributes and levels, to a spreadsheet-compatible file by clicking Data | Summary | Download Data. In addition to the general survey questions, you will find columns referring to the importance scores.