Take them out of the pots and very gently tease out the roots - if the plants have been in their pots for some time, their roots will probably be all tangled together. Gently spreading out the roots will help them get established. If you are planting next to a wall, it’s best to plant a little way away from the base of wall as it might be drier there, then lean the plants into the wall, if that makes sense! The plants will be at an angle to the wall. I usually leave the small cane in when I plant, as it does give the plant some support until it gets established. A handful of fertiliser in the planting hole is also a good idea. Once planted, water in to settle the plant. Hope this helps! My dear old mum loved Clematis and had loads in her garden.