1.) From your Office-365 Portal select the menu option "OneDrive"

(see figure 1)

Figure 1

2.) Select the document type you want to create.

You can even choose from these options without having installed Office on your computer since the appropriate web application automatically opens. Alternatively, if you do not want to create a new document but want to upload an existing file use the menu option "Upload existing file".

(see figure 2)

Figure 2

3.) By selecting the menu option “Share” you can make folders, documents or files visible and editable for other persons.

(see Figure 3)

Figure 3

4.) Now enter the e-mail adress(es) of the person(s) you want to share your data with.

(see figure 4)

Figure 4

More detailed instructions are provided here.