Go to ‘Invest‘ -> ‘Secondary market‘ section, choose an investment you want to purchase on the secondary market, and press the green icon ‘Buy investment‘:

After a successful purchase, the investment will appear in your Crowdpear account‘s ‘My investments‘ -> ‘Funded projects‘ section. You will acquire all the claim rights from the seller against the borrower, arising from the corresponding loan agreement (to repay the loan, pay Interest, late fees, and other related payments). There are no fees for the buyers in the secondary market.
In case you would want to sell an investment purchased on the secondary market, the option to sell the investment would be available only after 1 day after a successful purchase. Information on how to sell the investments on the secondary market can be found here.