If you are an international student and have not done so already, you should apply for a Study Permit from Immigration, Refugees and Citizenship Canada as quickly as possible. Detailed information about the process is provided by UBC's International Student Advising office.
An admission letter, even if it includes conditions, can be used to apply for a study permit. Applicants are advised to include an explanation letter which addresses how they plan to meet admission conditions. In most cases it is recommended to apply right away, even with a conditional offer letter.
If you believe that you will not receive the Study Permit in time for your stated program start date, please contact your graduate program to discuss the possibility of changing your start date and check additional considerations.
Make sure to read the important information about the recent changes to Canada's immigration regulations.