Citizenship is the last step in the immigration process of a citizen of another country. To do this, you need to meet the requirements of; 

• Be a permanent resident
• Have lived at least 1,095 days for five years before the date of entry of the application. If you initially entered Canada legally as a student, worker or temporary resident, these years are summed to the total number of days required.
• Not having any legal precedent inside and outside of Canada
• Tax return of at least three fiscal years
• Skills to listen and speak at least one of the two official languages of Canada
• Know the history, values, symbols, and institutions of Canada. The rights, responsibilities, privileges of a Canadian citizen.

Obtain the Citizenship could be under different situations.

• A Permanent Residents (PR) of Canada applying for yourself or your minor (under 18) child
• Past Canadian citizens who want to gain your Canadian citizenship back. 
• Canadians applying for citizenship for your adopted child born outside Canada

Qualified applicants can apply for Canadian citizenship. Once approved, they will be required to take a citizenship test (for candidates in the range of 18 and 54). Successful candidates will  then be invited to a citizenship service where they receive authentication of Canadian citizenship and authoritatively become new Canadian residents.

Information referenced from/to www.canada.ca