To prove the friendship you have to fill out settlement plan (Part 1) after being invited to apply (If your EOI is selected you will receive a letter of advice - I will use abbreviation in further discussion as LOA). Once you submit the application alongwith Settlement Plan 1, your sponsor (Friend, in this case) will receive an e-mail to submit Settlement Plan - 2 to ensure his/her eligibility (Residing in the province for atleast 1 year and is not currently sponsoring any other applicant).
Settlement plan has detailed questions regarding your connection like how you met? since how you know each other? any supporting documents might include pictures or a bit background about family members because Immigration expect that you know each other to an extent. Similarly if you have studied together (Like same school or worked together as colleagues) then educational documents mentioning names of school to find out whether your connection as friend is genuine or not. It all depends on your claim that how he/she is your friend? Another good supporting document might be screenshot of your friendship on facebook page which mentions how long you are being friends or any other information which shows that you know your sponsorship very well.
Another important aspect is that your CRS score does not help if you are choosing Manitoba PNP rather Federal's express entry program. Although you met the minimum eligibility for Manitoba PNP (Express entry stream) but in order for being selected for LOA Manitoba has its own points calculator. Please check the link
https://www.immigratemanitoba.com/immigrate-to-manitoba/general-mpnp-policies/sw-eoi-ranking/
The draw with lowest ever score for MPNP (EE stream) took place on 09th July, 2018 with 519 points. Please re-check your points on the link mentioned above since I am sure that CRS of 425 has no link with Manitoba points calculator.
